I think they think they're the only ones who truly understand, they're united against everyone on the outside who doesn't get it, they're armed with special knowledge and fighting the good fight against hostile and cruel -- or, possible worse, mundane -- outside forces. Andy seems to be good at tapping into that part of people that wants to be heroic and live an exciting life. And then he makes them into mere supporting characters in his own life, and it takes a while for them to realize what's happened.