Why are some girls so slutty?

Bother men and other women are extremely harsh on promiscuous women. They acquire bad reputations, look stupid, could contract diseases, and are at greater risk of ual ault if they're drunk. It can't be power, since most men don't date women who've slept with a couple dozen men. Why can't girls (and men) just date, have relationships, and break up with that person if it doesn't work out. Why would a girl disgrace herself by being promiscuous?