Many restaurants main menu is chicken or "FRIED CHICKEN", like MCDo, KFC Why?

I don't have any business similar to KFC OR MACDONALD.The reason people prefer these outlets is people like fried chicks.Though it might have a lot of calories this type of chicken is tasty hence people prefer it.When chicken isn't fried it will contain less oil and hence is good for us but people's work schedule makes them opt for a quick bite and this is convenient for them.