Women don't do booty calls?

It seems that if you want to sleep with a woman, you almost always have to be in a relationship first. Few women are interested in an NSA relationship or one night stand. They want to be wooed and awed. Why? I know I'm not the only one like me, as I've seen blogs from women like myself, and I see posts on the w4m section of Craigslist. So what gives?