I guess you mean solicitation and not actual prostitution? Unless they are putting up actual ads for callgirls, I’m pretty sure most of the solicitation happens via more private onlyfans and such.
At least in the USA, as long as they take down content as soon as it is identified, safe harbor should have them covered. Or maybe AI will make it super easy to tell teasing from an explicit offer to exchange sex for money.
Its very easy for these companies to identify and remove such content but for obivious reasons they dont do sadly