When people make a choice to do something, good or bad, it's their choice. Should anyone else feel responsible for it? No.
The choices people make are determined by their own character and mentality. If a person, for instance, needs money, do they steal? Or do they work for it? These choices are all determined by themselves alone.
You need money, you work. How hard you work depends on your character. If you're lazy, you don't work at all, you become a petty thief. If you can't stoop to stealing, you find something else that pays a lot for nothing (the concept of 'nothing' is also relative to the person).
You could become a mule (smuggling drugs for others), you could sell your body. The latter is more convenient, if you're the type who sees money as more important than yourself. I don't believe for one moment that one does not have a choice NOT to sell one's body. In this case, I'm talking about free-willed individuals, not people who have been kidnapped/trafficked and forced into this business.
Someone who'd rather work harder than he's ever worked in his life would rather clean dishes 18 hours a day in a dirty restaurant, even illegally, than sell his dignity. But then someone who'd rather sell their dignity probably doesn't value it.
It's a sad situation and I feel bad for people who feel they have to, but this is how some people are, and chances are, they don't feel as bad for themselves as you feel for them. Because everyone prioritises different things.
The choice you make is influenced by your own thinking, not the environment, not the situation, not by others.
There are always choices. We are all human, we have choices.
*Disclaimer: This post is about people who have free will and make their own decisions, not asylum seekers or victims of kidnapping and human trafficking.