He makes an interesting point that by withdrawing from larger society into sub cultures, people can return to dealing with groups of a size our minds are more comfortable with. It's the same reason small towns are (I hear) less socially stressful. I am not convinced though. In larger society I end up dealing with relatively small groups anyway - friends, family, and co-workers.
It seems pretty straight-forward that people would want focus on their interests and spend their time communicating with people that share those interests. It's definitely unfair and unfortunate that other people end up supporting them financially. With that said, we'll eventually have to come to terms with vast numbers of people not being economically productive anyway. People will have to do something. Withdrawing from society at large in favor of the parts of it that interest them seems like a fine choice.