While hair-pulling is often used as an expression of dominance over a submissive partner, especially a masochistic one, some people simply enjoy it because it feels good to them - myself being one of them. Pain and dominance have nothing to do with it. And I have occasionally ended up with scratches on my back so deep that they bleed, but that is because I have third degree burn scar tissue over 70% of it and I cannot feel sensation there unless someone gouges into my flesh, and even then it doesn't actually hurt.

No, there are not. It all accounts to raising and genealogy, but no one can say for sure which percentage of either accounts for behavior.