Nobody's wrong here... yes parents are shockingly, astoundingly lazy, both in their habits (driving vs walking) and their parenting (allowing the children to rule the roost because that's the path of least resistance - Let's call that the Drago argument). But yes roads are also worse and traffic / car ownership is higher, and drivers are more distracted than ever before (the Julia argument). It's the perfect storm for bringing up a generation of even lazier, even fatter, even more selfish people.
My daughter is 8, and just like pretty much everyone here I was walking to school unaccompanied at that age Monday to Friday and then playing out on my bike with my mates at all other times.
It's not possible to push your child out of the door now like our parents did in the 70s and 80s and simply say "don't come back until tea". There's a much higher chance now that you as that parent will get a call from hospital, or a knock from the police because they've been hit. What responsible parent wants to increase that risk?
No use saying "teach them", I've taught her, of course. But roads are much, much worse now, every pavement is blocked because of 3 and 4 car houses, there are distracted hassled Mums simultaneously driving Tabitha to school while checking Facebook and putting on makeup. Children don't always concentrate as well as they could. And they (we) never did concentrate all that well when crossing the road by the way, it's just that the chances of being hurt were much lower. Passing cars were rare, and the driver only had his eyes on the road.
All you can do is walk with him / her to school, accompany him / her on the bike, don't be in that selfish lazy percentile. Get him / her out on weekends for walks and treasure trails, bike rides, whatever, and limit electronic / lazy time. I think if you're doing that, you're doing more than 90% of "parents" and that's the best you can do.
I'm sad to say I think it'll all be in vain for the wider society, but at least you've brought up one person who can get off their backside.