You think that started in the 70s?
Yes. Definitely (though of course the actual specific time when such things started changes based on location, rural areas were slower than suburban).
Consider this: How old were your kids when you allowed them to go to a store by themselves for the first time?
How old were you when you were allowed to go to a store by yourself for the first time?
Ask your grandma how old she was. (Call your grandma anyway, she would love to hear from you.)