If you want your kids to grow old and you live somewhere where cars are priority you don't have much choice but your backyard, a park or wilderness. And a backyard might not be super fun/big and parks and wilderness aren't accessible without an adult.
I remember vividly when I was a kid and we were biking on the street and someone drove too fast, dad went out in the road and yelled him down, which was reasonable.
As I said elsewhere, my neighborhood had a whole copse of kiddos, including my own, playing out and about throughout the streets this weekend.
/shrug
Edit: I don't care about upvote tallies or karma count, but it does seem pretty silly to downvote a comment for pointing out that areas like this, and play in those areas, still exist.
I remember vividly when I was a kid and we were biking on the street and someone drove too fast, dad went out in the road and yelled him down, which was reasonable.