I joined years ago in pre-Web days at the time that I was looking for something to put on university applications aside from "reading". I think I was attracted by the "look how clever I am" factor as well. Apparently those are both reasons why lots of people apply.
I've stuck with the membership because I enjoy the magazine, though if I were better at socialising I think it would be much better value for money. It's not a bad choice if you're looking for somewhere with a wider variety of membership than the special interest hobby groups that mostly appeal to Aspies, but where you still stand a good chance of being accepted without any problem even if you come across as a bit quirky or hard to talk to.