Why would any woman without a drug problem be in the skin trade?

Over the past many days I have contemplated the premise of this question, and I wondered if one took the same modus operandi to the skin or sex trade. Why would any woman be a part of it? It is basically run by men (maybe not now), for men, and it was the men who got the lion share of the porno bucks no matter how many movies she was in. Even the highest paid porno actresses, I would bet did not make as much as a ‘B’ listed Hollywood actress. Off that same train of thought (not that it is right or wrong or the only way) why would a woman be a part of the sex trade if she had no drug problem to feed?