I do see that it is a little more dangerous to just let your kids run around unsupervised these days, or seems that way, with all the news reports of kidnapped kids, child predators, drive-bys, etc. But still, in my neighborhood, which is a pretty decent one, sometimes in the afternoons it's deathly quiet, almost like a ghost town. Lotta times the only people I see outdoors are the older 55+ yrs. ones, doing yardwork or gardening.
I think a lot of the parents who are in their 20s and 30s are lazy to begin with, and don't encourage their children to do anything that they aren't - namely, sitting on their ass, munching on potato chips, watching TV, playing Xbox, etc.