Nobody wants to deal with the short term issues it raises, aside from the moral police issue. Legalizing it actually increases trafficking in the legalized area, while reducing it in a larger area outside the legal one. This only happens because it’s an island of legality, if it was legal everywhere then trafficking would drop much more everywhere. But Nobody wants to invite the temporary increase by being the first. Germany, for example, has higher sex trafficking than most of Europe. It also ignore the difficulty of regulation, there’s a reason it is so prevalent, even where illegal. There is always going to be a strong pressure on vulnerable women, and enforcing the regulations can be incredibly difficult.

That’s not to say it shouldn’t be legalized. But these are the challenges it faces.