Hookers and Hookering

I know that I'm a day late and a dollar short when it comes to the Spitzer hooker thing.  I've been away for a few days and I'm sure there are already threads covering all aspects of it.  I'd like to throw my hat in the ring  anyway and ask a question that some of you wonderful people can answer.

I'm not necessarily advocating prostitution, but in the good year of our lord 2008, why does the government still regulate sexual activity?  If you can fuck other men, goats, whatever....why can I not pay for sex with a woman?  What comes to my mind is Roe v. Wade.  A woman has the right to control her body to the extent that she can kill a living thing inside her.  With that in mind, why can she not control her body as she likes and have sex for money?  Maybe those concepts are farther apart than I think, but maybe they're not. 

Is it because the government hasn't found a way to tax it it, or simply because its been on the books since the beginning of time and that's just the way it is?  I'm sure that it is still a "sin" by popular opinion but is that enough of a reason for it to be illegal?  It really seems like a strange "crime" since it isn't hurting or killing anyone and its not stealing anything....

Enlighten me