I live in an urbanized suburb (SFH, but 5 miles from a city core) and kids are out all the time. We have a few helicopter parents that feel the need to monitor their kids constantly, but for the most part, the parks, buses, restaurants, convenience stores, etc are all full of kids/teens. They don't even really cause trouble either. You'd think a group of teenage boys would be assholes, but nope, they just kind of mind their own business.

Once you get to the cookie-cutter subdivisions in the far suburbs, that's when the kids all disappear. Part of it might be helicopter parenting, but I think it's caused mostly by a lack of any outdoor activities. Riding your bike means going to the next subdivision over. Repeat that a half-dozen times and you get to a heavily trafficked road that can be followed for a few miles to a strip mall with a Target. Even all of the nice parks in these places are only accessible via car -- surrounded on all sized by 4-6 lane traffic going 45+MPH.