I think it is also partly fear. I know so many parents who are afraid to let their children out of their sight for even a moment. Not just the small children, either, but teenagers as well! People are so afraid of how other people are "these days." They hear news of child predators and then start seeing them around every corner. They are aghast at the fact that I will hike alone, ride a bus into the city, or strike up a conversation with a stranger.
I do see some hope with smaller home sizes starting to become popular again (rising heating costs, anyone?). I'm also seeing one friend's daughter playing more with children in the neighborhood, rather than only going on scheduled play dates. Interestingly, this change seemed to happen about the same time as their shift into more natural, whole foods prepared at home.