Alright, so prostitution. This is the absolute last step for a lot of people. And for good reason. We fearmonger that they have stds or cost a thousand dollars to get or even just that they're really fucking ugly. While some or all of these can be true for some, it is not true for all.
Here's why the rumors started though, and this is the kick:
The more people don't like something the more other people do it.
Weed wasn't illegalized because the government was afraid. It was illegalized because they could illegalize it. If stuff is illegal, then it simulates the economy. Higher prices. Higher chance of bad product. Bad product leads to doctor visits or needing checkup, which leads to steady employment rates.
War helps people out of depressions in their countries. It's the same concept as that. Illegalizing things, like prostitution, which are used in our lives (even if sparingly!) Causes problems. And the people at the top aren't stupid. They know if an std ridden druggie who got into a gang tries to rise up, they'll get stopped because they're weak. Less money for them means more money for the elites, because money only goes up.
We made our prostitutes illegal because they cost more, because they have stds, because they are ugly. If they were a legal industry they would instantly become less popular and erego less profitable to capitalism.