Legalization would make it much easier for escorts to coordinate on john screening. See for example the research done by Cunningham/Deangelo/Tripp on the effect

Legalization would make it much easier for escorts to coordinate on john screening. See for example the research done by Cunningham/Deangelo/Tripp on the effect of Craigslist shutting down their Erotic Services section. And that paper wasn't even on legalization, just a small piece of normalization that allowed coordination. There is also a paper by Cunningham on the accidental legalization of indoor prostitution in Rhode Island and its effect on crime and violence. Fascinating stuff.