I don't think bicycle helmets were invented yet when I was a child. Heck, motorcycle and football helmets were still made of leather, when I was a kid.

If bicycle helmets were invented back then, I never knew anyone who had one (or if they did have one, they kept it well hidden and never used it), and I don't remember seeing them in the stores or any of the bike shops in town.

None of my parents, grandparents, aunt's, uncle's, friend's parents, etc, etc, ever told me or my brothers, or cousins to wear a helmet when we were riding our bikes.
As far as I know, none of my friends were told to wear one, either.

When I'm riding a bicycle these days, I prefer to have a helmet. I know for a fact that the concrete or blacktop is a lot harder than even my head, should something happen and I'm involved in a crash.
When I'm riding my trike, I probably should wear one, but I don't.