ray_afraid said:

^Right. Which is why they can nickname someone Porkins even though there may or may not be pigs in space. It's for the audience to relate to. Like Han saying "I'll see you in Hell!" That doesn't necessarily mean there's a religion in that galaxy that believes in Heaven and Hell.

Right. Same reason someone can be called Droopy McCool or Wicket W. Warrick. It doesn't always have to make perfect sense. It is after all a set of films about fictional characters. I often wish the EU writers would realize this. I can't help but roll my eyes sometimes when I read about characters or species on Wookiepedia.
For example; you can get a pretty extensive analysis of the biolgy and appearance of the Sarlacc. I personally can't help but feel that we never needed an answers to these kinds of questions, and that many of them should never have been answered. I actually preffered to not know what a full Sarlacc looked like. I enjoyed the mystery surrounding the image of a large gaping mouth in the desert. It had a nice and weird fantasy feel to it. It was more about impact, than an attempt at realism. But now it's just another funky-looking animal that you can look up on a wiki.
You kind of lose some of the magic with this kind of over-analysis. It don't need a full explanation, it's not real life.