I can quickly say that we have outdoor educators, and they have identified that nature deficit disorder issue to me because people are tending to stay indoors and play with computers and computer games and video-type things. They're not going outside like they used to.
I think also there's a sense that parents want their children out in safe conditions, and they don't necessarily think that the world is safe out there. There are a whole bunch of things that are conspiring to result in what you've just described.