If you let a ten year old use transit themselves today, there's a decent chance parents will get a visit from the police. I think it's ridiculous, but that's how it seems to be.
Indeed; we learned this the hard way when I was growing up, in a graduate student housing complex consisting mainly of foreigners.
The one thing that dozens of nationalities could all agree on was their presumption that their ten year-olds can get home from school and fend for themselves for a few hours. Everybody knew everybody (quite literally), there were always adults out in the enclosed backyard, and there were periodic security patrols. I could think of few safer places to leave a child home alone. Until the harassment from the police started, it would have never occurred to any of us that this constitutes child neglect.
Conversely, I feel grateful that my parents chose to raise me in a dense urban area, instead of moving out to some suburban hellhole in an attempt to give me a bubble-wrapped existence.
I mostly took care of my own transportation to and from public school from the age of 10 onward (walking or public transit), and was never robbed, assaulted, kidnapped, conscripted into a gang, or whatever it is that suburbanites imagine happens to children in urban environments. I'm not a drug addict, I don't have a criminal record, and I'm gainfully employed.
I would never, ever raise a child in a suburb unless I had to for financial reasons.