When electricity was first invented and was introduced into the use of domestic environment, it was mainly for the purpose of bringing light to eradicate darkness. With more advancement it became an alternative for heating and also for using appliances to save manual labour-saving, as a means of creating a connection to the supply for other things apart from glowing up a light, the necessity of socket was felt. In the decade of 1920s, the two-prong electric plug was introduced.
Simultaneously, few electricity companies started to operate with a split tariff system to lower the cost of electricity that paved way for low wattage appliances which could be connected to the socket of the light.
As the requirement for more secure establishments grew, three-stick outlets were created. The third stick on the outlet was an earth stick, which was viably associated with earth, this being at the same potential as the impartial supply line. The thought behind this was that, in case of a short out to earth, a breaker would blow, therefore it could separate the electric supply and a life could be saved.
Now the question why the world is presently stayed with minimum 15 unique styles of attachments and divider outlets is that, on account of numerous nations wanted to build up their very own fitting, rather than embracing the US standard because the wobbly American plugs with their uninsulated prongs have become obsolete and aren't that safe to use.