Very. Although it always depends on the film. I think Lord of
  the Rings is an all-white caste (the elves and wizards being the
  extremes of whiteness) - I dont' know if they got asked the same
  question. Although I don't know what a good answer to that
  question *would* be, really. "Because we did." - one of those
  answers that uses the question for the answer - is about the
  only way I can think of to answer it - and even that's not a
  "good answer". What do you think? "