[qvdutlrl] Shared practice as a social barrier to entry

One of the Catch-22s of social partner dancing is, people don't want to dance with you if you're not good at it, and you can't get good at it unless you dance with lots of people, especially dancing with people who want to dance with you -- there is a subtlety in whether you can or cannot learn with someone who is not really enjoying dancing with you.

The way the paradox is avoided is that people may want to dance with you for reasons other than you dancing well: for social reasons: they like being around you for reasons other than your dance ability.

In this way, social barriers are unofficially institutionalized and magnified, but no one has to feel bad about it.  No need to put up a "Whites Only" sign, even though it has de facto occurred in many dance communities.

What other institutions of segregation rely on similar feedback mechanisms?