I have my doubts that prostitutes are victims kept against their will. One can discuss if the legal limit for prostitution should be 21 years. Should same be true for soldiers then?
Prostitution is a very complicated phenomenon. There are definitely many women for which prostitution is a choice and a way to make a living.
But there are also many (especially foreign) women who are brought into prostitution by a combination of threats, intimidation, shady debts incurred in irregular circumstances, etc.
It's extremely hard to make a one size fits all for these two very different groups.
With all due respect, no woman really "chooses" to go into prostitution and sell their bodies. For one reason or another they are more or less forced into it because it may be the lesser of two evils. I actually became friends with a woman that was "formally" in the sex business and it was the worst two years of her life. I do think that is cases of prostitution it is fair to only prosecute the man, as the woman is considered a victim. She is being taken advantage of in a position of weakness, which is human trafficking.
I got curious if what you say is true in India and read Ashok Alexander's "A Stranger Truth". The book is of 2018, but he tells his story about leading the Gates Foundation's HIV prevention program in India for 10 years from 2003.
His father was already a big shot in politics and he also had quite a position at McKinsey. It seems management and navigating Indian politics was the tricky part, for he had never worked in this area before. His team had to contract capable NGOs or other organizations on state level working in that field. That NGO in turn subcontracted to local NGOs. He didn't write much in his book about politics. Did he or the state level organization have to manage state level politicians?
Surprisingly prostitutes were not mainly concerned with HIV, but with violence from police, customers and boy friends. There are really ugly stories. A rather mild story, but probably quite common: One prostitute told how she tried to convince a customer to use condoms. She said she may be HIV positive and that he has a wife at home who loves him. He slept her hard, threw a lot of money on the bed and and commanded "Spread your legs, bitch." Fearing further violence, she obeyed.
The trick was to organize commercial sex workers. United they had more power. While the local organizations mostly employed sex workers to reach out to other sex workers, about 10% was other stuff in charge of management, law... Together they approached police commissioners to complain of violence by policemen. They organized themselves to fight back violence of boy friends/ customers.
Somehow violence decreased a lot and condom usage increased a lot. The Gates Foundation managed to arrest a potential epidemic.
Two things I want to add.
1) Neither Roland Girtler from Vienna nor Ashok Alexander from India seem to find any faults with the sex workers. It's probably good. If these people trust sociologists/ other scientists which later write disagreeable things about them, their willingness to cooperate may reduce in future. Girtller as sociologist also can't spoil his contacts. And Ashok Alexander now runs another NGO. Potential donors may read his books.
Both books are good. I just mean to say one has to see the limitations.
2) The abuse started much before sex work. Reading some of the live stories I felt the fathers had the empathy level of Joseph Patrick Kennedy lobotomizing his own daughter. Also there seems to be a lot of alcohol abuse among prostitutes, but also their fathers. Ashok writes that prostitutes are excellent judges of characters within a very short time. That's something known from psychopaths. So I guess, but may be wrong, that antisocial/ narcissistic/ borderline and histrionic personalities cluster in their families. I speak of increased probabilities.
Obviously that's not written in the books. It's what I read between the lines.
Prostitution in cities had a lot of abuse, while prostitution with truckers was mostly cordial. It's mostly long distance truckers who go to prostitutes. A long distance truck may have two drivers and young helper. It seems the alpha trucker sometimes bargains a package for all three.
Not written, but my interpretation: it seems to be a way of life and truck driver customers may have much more variation in character than customers in cities. Or maybe customers in cities go to prostitutes for stress relieve while truckers relieve boredom? I don't know.
Can you expand what your former prostitute friend has to say?