That may have been true in the 60's, but there are too many fast dining alternatives today for that to be the entire reason. The deciding factor for McDonald's among many nearby restaurants is just as I said: reliability, consistency, predictability, price, promotion and preference for the menu items.
Consistency?? No way.
Wanna talk consistency, price and preference, try In and Out Burger. (the BEST period)
McD's changes their menu too often and frankly, has too much. It should have only featured, Hamburgers, Fries and drinks. Maybe add the McNuggets and basic breakfast for variety's sake. The rest should have been dumped, or just never added. Too much is not good either.