Plenty of hikikomori in the safe, walkable Tokyo. What's keeping them inside?
I would guess they've shut themselves in and away from the shame and rejection by society and have found the tiny inkling of happiness possible in that hole. And as society continues to rejects them further for being in a hole, the hole only gets deeper.
Understandable, since the minute they go outside, everything is stacked against them and even with help, they probably won't be able to compete on the same level as the normal people who didn't fall into the hole. I can't win outside, but I can be happy in my hole. Hole good, outside bad.
You sound like you're making an excuse for a lack of friends by implying there is no one worth being friends with? Perhaps I've inferred too much, I sure hope so...