I think half is really really optimistic; Steinem has often quoted statistics about the horrible increase in physical violence directed toward women, especially in the U.S. but all over the world, and this is particularly evident in the sex trade. See this article.
Studies have shown that the majority of the customers aren't there for a companion; they're often violent. For the most part, this isn't some high-class call-girl version of Pretty Woman. They get beat up. A lot. Especially if they're trans.
A lot of them are homeless teens who have no other choice.
It's sad that our social programs are so lacking, or that our society is so stupid and uncaring, that people are forced into such degrading circumstances. I've been watching that show "I am Cait," and several of the trans women that Cait talks to at the Human Rights Campaign in San Francisco told stories of having to resort to sex work because they lost their jobs because they were trans and they couldn't find another job and they had to survive, and several were severely beaten. One woman said she was beaten and then the man drove away but then she heard his car come back and she realized he was coming back to run her over with his car.
But, not all "sex work" falls under these categories, obviously. There are different levels, and it would be hard to make any kind of one single sweeping legal change that makes any sense from the real feminist perspective (supports choice but also supports oppression and violence against girls and women).
Well, exactly, yeah.