There's a huge difference between picking up a streetwalker, going to a legal brothel, or answering a personal ad in places like Canada where it's a grey area if it's legal
Like, off the street there's probably some coercion somewhere, legal brothel it's less likely they're forced to do it but it might still be trafficking but there's likely at least some form of oversight, and personal ads are a total crapshoot. It might be someone who's selective and just making some money, it might be someone that has to accept every offer.
When things arent 100% legal, some shady is statistically just going to happen. You can't regulate an illegal business.