[coldtea]

>The reason that they do so is not entirely clear.

Not clear? It's almost too clear as to be tautological.

They do because they (a) think all members should have equal say, (b) most members in the group want X to be done.

Unless we're talking about submitting to force or listening to expertise, why would many people wanting to do something, let fewer people tell them what to do instead?

Heck, if it comes to fighting for what's to be done (the most effective but primitive form of getting a decision), the majority could beat up the minority and have its way anyway.