<blockquote>The main question is - why coerced prostitutes are not going to law enforcement? What prevents them? Will they be deported for that?</blockquote>
They or the people they left behind to report the people running them will be beaten and possibly killed. People who are illegally importing sex workers aren't nice people who will just ask them not to go to the police again.
This problem probably can be solved with technology - make Airbnb for amateur sex workers :)