Because if its legal then the industry can be regulated to insure the safety of women working in it. But as long as it’s illegal there are no regulations, and no one sex workers can go to for help because they’re working illegally. It’s also known as the worlds oldest profession; its not going anywhere. And as someone who knows a lot of people who are pro-prostitution legality, they aren’t the people you seem to think they are. They’re all kinky queer folks. The folks I know who are most ardent supporters of the idea are women, some of whom are sex workers themselves just producing content rather than working as prostitutes.

Its an industry that always has, and always will exist, and if you legalize it you can protect the people working in it.