I think the answer is increase an increase in demand for the stocks of similar companies. If all similar stocks would increase, the effect would also increase the stock price of a company. This is could be in consideration of sudden changes of factors in the market that gave basis for price increases. This might have created a standard of near prices for similar stocks.
I think because no other country in the world has created something interesting or it was just a pass down by their ancestors and they wanted it to be a thing
