How we ended up with 15 different kinds of plugs and sockets?

There is 15 different types of power plugs and sockets in the world and those are named with letters from A to O. Main question is why we have those 15 different types of power plugs instead of one in whole world. All of this plugs works either with 50 Hz frequency or with 60 Hz and the voltage variate between 100 to 240 V. Around 80% of all the countries in the world use voltage between 220 to 240 V and the rest 20% use voltage between 100 to 127 V. Although the biggest user of lower voltage United States of America has started to use 230 V split in two 115 volts wire and that allows every possible appliance to plug in without concern of braking it. So maybe some point in future we only have one short voltage area. (International Electrotechnical Commission 2015), (H.McGregor 2015).
Some history to this point to give a hint why we even end up needing these power plugs and sockets. All of this goes back to man named Joseph Swan who invented incandescent light bulb in 1878 and Thomas Edison who invented indoor light bulb which was huge invention at that time. Light bulb was huge invention at that time people were able to see in the dark house without candles. After many test and disappointments Thomas Edison was able to create lamp that lasted 13,5 hours 22nd of October in 1879 and he filed a patent for it and so it was the first commercial incandescent light bulb.
After patenting the light bulb Thomas develop a way to distribute electricity to compete with gas distribution and founded company named Edison Illuminating Company. He switched on his first electrical power distribution center in 4th of September in 1882. It provided 110 volts of direct current aka DC for customers in Manhattan. When he was expanding his distribution network his competitors started installing alternating current system and pressuring his company a lot. (Thomas Edison 2015) (Incandescent light bulb 2015)
Nikola Tesla the cofounder of modern AC electricity supply system started working in Edison´s company in 1882 in France and moved to New York in 1884 to work in his Edison Machine Works. Thomas offered Nikola a task to redesign their DC generators. After Nikola was done he asked about his payment and Thomas said that he was just joking about that $50,000 he had promised. Tesla resigned from the company in 1886 and started working with Robert Lane and Benjamin Vale who promised to finance electrical company in Tesla´s name. By the 1888 he had invented two-phase induction motor which AC systems had missed until then and this is the base of our current electricity supply system. (Nikola Tesla 2015) (Alternating current 2015)
With the help of development of transformers alternating current became cheaper option because they were able to use thinner wires and lower the voltage at the end of the distribution. This made possible for AC companies to start delivering to smaller cities which was not possible for Thomas´s company. Competitors built their first alternating current distribution center in 1886 and by the end of 1887 Thomas has started to lose his share of the market. Few people died because of pole-mounted high voltage AC lines and Thomas started to campaign against the AC with the help of electrical engineer Harold P. Brown. Their objective was to get through legislation that would limit installations of alternating current by showing that AC was the best current to power the brand new invention the electric chair. Despite all of their efforts they could not do it and during 1890s Thomas left his company and company started to add AC to its technology as well. (War of Currents 2015) (Thomas Edison 2015)
Around the same time first plugs were invented already in United Kingdom but they landed to North America when Harvey Hubbell II invented electrical power plug in U.S. in 1903. Why that plug was needed then? Answer is pretty easy actually because of the split-tariff system which meant that electricity was cheaper when it went to lighting so then it was needed to have a plug and socket for other appliances also to reduce the electricity cost. Simple reason like always cutting the costs of electricity.
Following paragraphs will be about different kind of types of plugs and sockets. Some general information about all of them also why they were made and when if it is known.
Type A (see fig. 1.) was actually invented by Harvey Hubbell II in 1904. It is not the first plug/socket system ever invented but it is the oldest one still in use. Socket however is too unsafe so it is pretty much extinct because type A plug works with type B socket which is grounded. This could have been the one everybody uses but unfortunately all the other industrial countries saw this too unsafe and decide to develop their own. It is used in North and Central America plus Japan. (International Electrotechnical Commission 2015)
Type A normally has voltage between 100 and 127 V and it is rated as 15 A. It is also not grounded unlike it´s so called sister type B and it has 2 pins as shown in picture. Socket is only compatible with this type of plug. (H. McGregor 2015) (Figure 1)

Type B (see fig. 2.) is based on Type A. It was invented and patented by man named Phillip F. Labre in 1928. He deduced because of his landlady´s cat that electricity would rather go to earth than person and that is how he invented grounded plug. So difference between A and B is that B has 3 pins instead of 2 and that third additional pin is the earth which means that plug is grounded. (International Electrotechnical Commission 2015) (AC power plugs and sockets 2015)
Voltage is between 100 and 127 V usually and it is also rated as 15 A. It is used in North and Central America plus Japan. Socket is compatible with Type A and B plug instead of socket of type A which is only compatible with Type A plug. (H. McGregor 2015) (Figure 2)

Type C (see fig. 3.) is One of the most common used plugs in the world and also one of the oldest plugs still in use. Socket of this type is restricted in almost every country by now but plug is as said one of the if it not even the most used plug in the world. This is also an example of plug that fits Europlug standard. Voltage is between 220 and 240 V and it is rated as 2,5 A. It has 2 pins and it is not grounded. That means that nowadays type C sockets cannot be used in new buildings almost everywhere. It is used in Europe with exception of United Kingdom, Malta, Cyprus and Ireland. The plug itself works perfectly with socket of types E , F, J, K, and N. Socket of type C works only with plug of type C. (H. McGregor 2015) (International Electrotechnical Commission 2015) (Figure 3)
Type D (see fig. 4.) voltage is between 220 and 240 V and it is rated as 5 A. It has 3 pins and it is grounded. Socket is compatible with type D and C safely and unsafely with E and F. (H. McGregor 2015)
It is used for example in India, Nepal, Sri Lanka and Namibia. Plug was previously used in United Kingdom until the World War II ended and they decided to develop a new plug type G. Type G replaced type D in new buildings by the end of 1950s and by the end of 1960s it replaced all remaining type D in whole United Kingdom. It was originally invented because United Kingdom did not want to start use American standard plug type A because it was unsafe and it ended to India because at that time it was under British command. It ended same way too many other countries that were under British command in 1930s, for example Ghana, Pakistan and Nigeria. Reason for this type to spread is pretty much United Kingdom. (H. McGregor 2015) (International Electrotechnical Commission 2015) (List of national independence days 2015) (Figure 4)

Type E (see fig. 5.) voltage is between 220 and 240 V and it is rated as 16 A. It has 2 pins and 1 female pin and it is grounded. Socket has extra man pin where that female pin from plug fits. Socket is compatible with plug types of C, E and F. (H. McGregor 2015)
It is used for example in France, Belgium, Tunisia and Slovakia. It is variation of type F which is believed to be invented in Germany by Albert Büttner in 1925. It was invented either in France or Belgium and most of the countries that use it were under French command at the time of invention. It also appears to be in use in countries that use type C as well because its plug is compatible with this type of socket. (H. McGregor 2015) (International Electrotechnical Commission 2015) (List of national independence days 2015) (Figure 5)

Type F (see fig. 6.) voltage is between 220 and 240 V and it is rated as 16 A. It has 2 pins and it is grounded. Socket is compatible with plug types of C, E and F. (H. McGregor 2015)
It is believed to be designed in Germany by Albert Büttner in 1925. It is used in whole Europe and Russia except United Kingdom and Ireland. Reason why this spread to so many countries in Europe is actually pretty simple. Its socket is compatible with type C plugs which were really common in 1930s and the positive thing is that this socket is grounded compared to the type C socket which is not. (H. McGregor 2015) (International Electrotechnical Commission 2015) (AC power plugs and sockets 2015) (Figure 6) Type G (see fig. 7.) voltage is between 220 and 240 V and it is rated as 13 A. It has 3 pins and it is grounded. This type socket has almost always switch for extra safety. Socket is compatible only with type G plug. (H. McGregor 2015)
It was first seen in 1946 and standardized by 1947 in United Kingdom. They used type D until World War II but after getting bombed by Germany they had to build everything from a scratch so they decided that they need new plug. It is used for example in United Kingdom, Ireland, Malta, Malaysia, Singapore and Hong Kong. Reason why it spread to many countries is that they were still under British command for a while after World War II so they got to adopt this system. For example, India that gained independence in 1947 did not have the change to adopt this so they got stuck with type D. (H. McGregor 2015) (International Electrotechnical Commission 2015) (List of national independence days 2015) (Figure 7) Type H (see fig. 8.) voltage is between 220 and 240 V and it is rated as 16 A. It has 3 pins and it is grounded. It is exclusively used in Israel. Socket is compatible with plug types of C and H safely and unsafely with plug types of E and F. It was only compatible with type H plug until 1989 when they made those round shapes in the socket so type C for example can fit in. It is exclusively used in Israel. I really do not know why they decided to make their own and frankly I cannot make any sense to it either. (H. McGregor 2015) (International Electrotechnical Commission 2015)

(Figure 8)
Type I (see fig. 9.) voltage is between 220 and 240 V and it is rated as 10 A. Type I can be with 2 pins or 3 pins and it is grounded when it has 3 pins and not grounded when it has 2 pins. Socket is compatible only with plug Type I. (H. McGregor 2015)
It is used for example in Australia, New Zealand, China and Argentina. It is actually called as Australian plug because it was made in Australia. Dimensions of this is almost completely same as type A and it is not a coincident because it was made based on the old American standard patented by Harvey Hubbell II in 1916. Difference between type A and this was the fact that this had 3 pins against 2 in type A. Americans did not like this plug because it was incompatible with existing type A. Australians favored this type over British Type D because it was easier for local manufacturers to produce flat pins than round pins. Australian electrical accessory manufacturers and State Electricity Commission of Victoria standardized Hubbell’s design in 1930s. After that it was adopted by nearby island countries, China and Argentina. (H. McGregor 2015) (International Electrotechnical Commission 2015) (Figure 9) Type J (see fig. 10.) voltage is between 220 and 240 V and it is rated as 10 A. It has 3 pins and it is grounded. Socket is compatible with plug types of C and J. It is used almost exclusively in Switzerland and Lichtenstein. I think Switzerland decided to develop this plug system because they thought it would be universal and so used in every country but it turned out to not be it so they ended up using it almost by themselves. (H. McGregor 2015) (International Electrotechnical Commission 2015)

(Figure 10)
Type K (see fig. 11.) voltage is between 220 and 240 V and it is rated as 16 A. It has 3 pins and it is grounded. Socket is compatible safely with plug types of C and K and unsafely with plug types of E and F. (H. McGregor 2015)
It is used almost exclusively in Denmark and Greenland. Denmark did not want to start using American standard because it was unsafe so they also decided to develop their own. It is expected that type K will be replaced in Denmark most likely by Type F or less likely by Type E. It was spread to Greenland and Faroe Islands because they were connected to Denmark in Danish Realm in 1948. (H .McGregor 2015) (Danish Realm, 2015) (International Electrotechnical Commission 2015) (Figure 11)

Type L (see fig. 12.) voltage is between 220 and 240 V and it is rated either 10 A or 16 A. It has 3 pins and it is grounded. 10 A socket is compatible with 10 A type L plug and type C plug and 16 A socket is compatible with 16 A type L plug. (H. McGregor 2015)
It is almost exclusively used in Italy and Chile. In the beginning of Type L usage, it was only compatible with Type L sockets but later was decided to make socket compatible with Type C and Type F/E so new socket were made to accomplished the target. Socket has two parts one for Type C and one for Type F/E. (H. McGregor 2015) (International Electrotechnical Commission 2015) (Figure 12)

Type M (see fig. 13.) voltage is between 220 and 240 V and it is rated as 15 A. It has 3 pins and it is grounded. Socket is compatible only with type M plug. (H. McGregor 2015)
It is used for example in South Africa and Swaziland. It is almost similar than Type D but pins in Type D are much larger. Type M plugs are in some cases used in Type D and Type H countries. For example, in United Kingdom they still use Type M plugs in theater installations. (H. McGregor 2015) (International Electrotechnical Commission 2015)

(Figure 13)
Type N (see fig. 14.) voltage is between 220 and 240 V and it is rated either as 10 A or 20 A. It has 3 pins and it is grounded. Plug made for 10 A and plug made for 20 A are otherwise similar but the pins diameter is little bit bigger in 20 A-version. Socket is compatible with plug types of C and N. (H. McGregor 2015)
It is used mainly in Brazil but also in South Africa. It was published in 1986 by International Electrotechnical commission. It is called the universal plug which was supposed to main plug in whole Europe and in countries with voltage of 230 V. Unfortunately, economy crisis in mid 1990s stopped that attempt while countries were not interested changing plugs when there were way more important issues at hand. (H. McGregor 2015) (AC power plugs and sockets) (Figure 14)

Type O (see fig. 15.) voltage is between 220 and 240 V and it is rated as 16 A. It has 3 pins and it is grounded. Socket is compatible safely with plug types of C and O and unsafely with plug types of E and F. (H. McGregor 2015)
It is used exclusively in Thailand. It was invented in 2006. It has not yet been assigned a letter code which means it is not in IEC list but it is standardized plug. (H. McGregor 2015)

(Figure 15)
Why we ended up with so many different kind of plugs then? Well it was all about the timing to have the need of plugs and sockets. It all started early 20th century when electricity companies used split-tariff system to sell electricity, which means that it is cheaper to buy electricity only for lighting than to any other cause. Because of that portable appliances were created and plugged to light bulb sockets to get cheaper electricity costs. Electricity became more common method to use appliances which brought the need of other way to connect to the electric system than light bulb socket. (AC power plugs and sockets 2015)
The first plug and socket were introduced in 1883 in England by T.T Smith but the first patented plug/socket system was introduced in 1903 by Harvey Hubbell II. That is more or less type A plug/socket system which is still used in North America for example. Well not quite because in 1928 Phillip F. Labre invented grounded version Type B which is nowadays the one that is mostly used in North America instead of Type A. Grounded plug/socket system became compulsory in almost every industrial country because of its safety compared to system that is not grounded. (AC power plugs and sockets 2015)
S-curve model does not really work for power plugs there was not really a previous technology to rely because it was a new need and there has not been really any kind of evolvement in the technology since they realized that plug system should be grounded so I will not put S-curve here but I will put something that shows when these systems were invented.
Invention of some types are still kind of in the dark. There is no information about when they were invented but I guess that is somewhere between 1903-1940. I could not find reliable information anywhere so I will not make the invention year by myself.
One of the main reasons why so many countries decided to develop their own system in early 20th century was the unsafety of United States standard. It was even then unsafe and it has not change a lot in almost a decade so no wonder why so many countries decided to develop their own. Question is why they did not decide to do it together instead of working alone. (H. McGregor 2015)
The first discussion about standardization started around 1930s which was sadly interrupted by World War II and put ahold till 1950s. During that time many new socket systems were invented for example new British plug nowadays called plug Type G in 1947 which made standardization even harder. By the time discussions started again so many new countries had already started to use this plug or that plug and because of that standardization became almost impossible. Basically they already managed to build their infrastructure so far that they were not interested to change it anymore. Companies decided to provide either to national or regional markets. (International Electrotechnical Commission 2015)
Type G was invented after World War II which was not so long ago and still they decided to build completely new system without involving anybody else at all. Anyway it seems that some countries still live in 1950s and do not know how to share and loan because Thailand decided to develop their own system in 2006. This is the attitude which was in lead in 1950s and apparently pretty much still in 21st century. It is one of the biggest reasons why we have now 15 different kinds of plugs in the world. Countries only cared about themselves, there was no communication between countries like there is now. Multi-national corporations did not exist yet or those were still in its infancy to help move the information about plugs or any other things. Cold War did not help either in this case freezing relationship between East and West for decades. (John Herman 2015) (AC power plugs and sockets 2015)
In 1986 IEC which is International Electrotechnical Commission actually published international standard for a universal plug. Idea was good it was just give or take 40 years too late at this point. Most of the countries had already been using their plug for at least decade which meant that their whole infrastructure was finished and they did not want to change to use some different kind of plug just because it would make things easier. That size of change would have cost to any country billions of Dollars. Brazil and South Africa are the only countries that have adopted this universal plug type N so far and Brazil was first one in 2007. (H. McGregor 2015)
I can say for almost 100 % certainty that in my lifetime standardization of plugs will not happen. Maybe using some other way like USB it might happen in the future but I am pretty skeptic about it.
So all in all reason why we have so many different plugs and sockets is not just one thing. One of the reasons is timing. Plugs and sockets became needed in early 20th century and then came World War I and it made situation harder and just when things started to settle came World War II. It was not the best time to try have something universal in the world because countries did not trust each other at all. Cold War after World War II did not make it any easier so I am not actually even surprised that we have 15 different kinds of plugs and sockets. If we would have invented this thing now I think, we may have survived with 3 maybe 4 different kind of systems but still not only with one. It is noble goal but I think it is unreachable for this generation and it was for previous generations also. Also we have the problem of different voltage in some countries which made harder to find universal plug even though nobody was even thinking of it. Travelling was not really a thing back then and because of that no one actually cared about which kind of plug they use over there. Main reason for this is that we just happened to invent something really important in the worst possible time in the history of mankind. Well this is not the actual reason because the reason is all those wars, lack of travelling, difficult relationships between some countries and so on. I could pretty much continue this list forever but the thing is that we are humans and we make mistakes. It is human to have 15 different kind of plugs in the world and maybe sometime in future we may have less than that but it is not the problem we need to be dealing with right now considering everything that is going on so I think we will have those plugs still for a long time.
In making this submission I declare, that my work contains no examples of misconduct, such as plagiarism, collusion, or fabrication of results.