Because we don't reach out to our neighbors the same way anymore, because they already have lives as do we. It's a self-reinforcing trend.

I suspect the origin of the trend was, once we had the freedom to select friends out of a greater geographic region we happily did so, because there really is no guarantee the ten people living nearest to you are into the same things you are.

We're not talking about whether you should visit your friends, but whether you would elect to walk...