When something is legalized, it's taxed to death. But being regulated by a government could mean better health care for people in the business. This could cut down on the spread of sexual diseases by sexual workers.
On one hand, the idea that prostitution is illegal in the first place is incredible. You're a criminal for selling something you're perfectly legal to give away.
But on the other hand, because legalized sexual workers would inevitably bring more taxes on the service and less anonymity, the sexual service underground would be worse. More inexcusable and more dangerous for the workers caught up in the illegal underground that doesn't conform to whatever standards the government would impose on the market.