I'm not sure that they haven't. I would imagine that for people who frequent places like this (and strip bars too)the objectification of women is part of the appeal.
Contrary to what Amber writes, I also very much doubt that women who consider themselves feminists or liberated would actually work at a place like this... though some may tell themselves that is the reason in order to be able to live with what they are doing. To me, and I hope many others, 'liberation' is about equality and respect. I don't see respect in any shape or form in places like this.