system
Given the following post, respond as if you're commenting on Reddit:
human
Why is prostitution illegal?

Let's say I want sex and am willing to pay $20 for that. There's a woman who wants $20 and will have sex for that. Why can't we make each other happy? Who is being hurt by prostitution? I understand why pimping should be illegal, but why straight-up prostitution?
gpt
Prostitution hasn't always been illegal in the US. Look at the stories of the Wild West and the "dance hall girls." Tell me Ms. Kitty wasn't a madame. 

Along around the turn of the 20^th century, women started looking for causes to support. The idea was that if women could make a social change, they would be granted the right to vote. Among some of the changes that women proposed were public education free to all children and mandatory for them. Improved laws to control drunkenness. And the point of your question, laws to control the exploitation of women. 

In the 1890's as rights were being fought for over the newly freed slaves, women didn't have many rights. In a lot of places they couldn't own property or argue in court. That left women without a man to take care of them in a bad situation. A lot could not find work in the factories, and working the fields was left to those who owned the land and could hire workers, so that left selling the one thing that women were born with. 

It was exploitative because the laws were shaped to not give a mature single woman any chances. Add to that the fact most were uneducated because public education was still a few years off and you can see the trouble these women would end up in. 

There were plenty of men who would take these women under their support and expect them to earn a living for them in the only way they could. Prostitution. 

Some of the women looking for social causes to support decided to fight for the rights of the exploited women and make prostitution illegal. The idea was that if selling sex was illegal, the women would have to be accepted into the traditional workforce. That idea was a lot slower coming than making sex workers criminals. 

The reason prostitution is still illegal is mostly moral. The guys (and now women) who make the laws will have a hard time campaigning on a pro-prostitute platform. Everybody wants prostitution. Nobody wants it in their back-yard.