Well, I would frequently walk or bike to school in jr high. Did it a few times in high school. Never in elementary.
The walk for me as a half hour, and it's only halfway across town. No sidewalks through most of it, residential neighborhoods but moderate traffic as people are going to work (or school). Never had any significant incidents, and knew plenty of people along the route I could have sought help from.
Now? No way would I let my kid walk to the same school. More traffic, more assholery, and kids just aren't treated the same when they're walking alone. It isn't even about risk per se. The area is populated enough, with enough adults around, to make anything but really fast snatches improbable. That was always a risk.
It's about the reality of what a kid in their tweens is going to see and hear. The kind of perfectly legal but unacceptable bullshit they'll run into. Assholes of all ages, everywhere. I trained my kid the handle most things, but they shouldn't have to.
And the walk to the high school is over twice as far. So even after the extra development might give a kid the ability to handle the shit, there's more chances for it to happen.
And it sucks. I had freedom to explore my town. To get the exercise, the sense of community from waving to and being waved at. But nowadays? Too many assholes. Even if I was able bodied again, I wouldn't fucking walk the same route, armed and trained as I am. That last part less because I'd be worried about someone fucking with me, more that I'm a grumpy old fuck and might not keep myself as restrained as I used to.
I wish like hell my kid could have had that experience, but those days are gone. With the added bullshit of the nanny state deciding that walking on public streets isn't safe and that's somehow the parents' fault, it wasn't worth or, and I don't see that changing until we have a cultural shift back to having a sense of community and connectedness. We don't have to like each other, but we do need to watch out for each other, and that's harder to find than it used to be just 40ish years ago.