Prostitution can get both the customer and the prostitute imprisoned for up to 15 days. It has been used as an excuse for arbitrary arrests and detention of dissidents. I have noticed the same sort of spam on Twitter. Every time some dissident tweets something unflattering about the CCP, it gets spammed by “replies” advertising sex services or pornography to draw people away from the political issue. I have no idea whether those are “legitimate” sex services. They probably aren’t. Doesn’t matter. The credibility of the tweet is compromised.