Criminalizing sex work puts its management in the hands of criminals, promoting slavery and abuse. Legalizing sex work allows workers to create safer working conditions and take the management away from organized criminality. Regulating and regularizing sex work allows for health/communicable disease screening, taxation and workers benefits (health care, retirement). It also takes a big weight off of the criminal (in)justicel system. There is no legitimate reason to criminalize sex work other than forcing your own (often hypocrytical) morality on others who do not share it.