I think that - unlike many gyms and other fitness communities - it's very welcoming to non-conformistist and people who don't look like typical gym junkies.
It's hard to have an ego when just about everyone gets outclimbed by 12yo girls, and the best climber in the world looks like someone who got fired from a big tech company because he looked too geeky: http://www.alpinist.com/doc/web16f/newswire-ondra-dawn-wall (and I love that even he failed to replicate Lynn Hill's "free climb The Nose in 24 hours" - apparently even Ondra needs to practice Changing Corners).
Also, bouldering in particular is such an intellectual pursuit. It's problem solving under physical pressure, and forces you to think hard about the geometry of your body and how weight works etc.