Do people with these weird fetishes draw upon the same urge that makes normal people make porn/etc. or does having these fetishes make them more inclined to show the public how "great" they are? As far as I know, there are no men running around doing talent shows loudly proclaiming how great it is to vigorously thrust penises in vaginas (well, no one besides closeted Republican congressmen).
Half of them are probably into the exhibitionism aspect, the other half are into the humiliation aspect. All in all, going on stage is a win-win for them.