Prostitutes wouldn't have to worry about getting beat up by pimps or customers. There would be no legal backlash against the women trying to protect themselves. Disease is also an important factor. If prostitution were legal, then the government could also go around and test the prostitutes for AIDS and other diseases. They could subsequently force them to get treatment to prevent spreading diseases.
Suicide is a crime in most states.
I know it is against the values of every religion, unless you are performing ritualistic Hara Kiri, but our nation doesn't get its laws from religion, or at least it shouldn't. Look, if some schmuck wants to lose his house at a card table because he has no self-restraint, that's his business. Like prostitution, legalizing gambling would stop people from being killed because of bets. Bookies could repossess your house instead of fitting you for a pair of cement shoes. If a woman wants to have more than one husband, more power to her.