There are other reasons why they won’t collaborate with you. I can tell you why they won’t do so with me, though: simply because I choose a specific theme and expect my teammates to do the same. That doesn’t sit well with their own plans, or with the plans of the person who sent them to me. So I’m a no-go, as there’s no way to give the ‘home clique’ an upvote without me seeing it and saying something about it.
If you want to work with people like that, you’d have to be either deaf and blind, or incredibly stupid, or greedy enough, or corrupt.