My belief is they do it because they know themselves they are skanky, nasty, ugly and desperate so they do this as their hook to get guys through the door.
The problem is, they don't then usually do it, or anything bar sit there like a sack of potatoes miserably, so all you get is some skanky nasty and desperate girl who is offering a terrible service.
Basically my advice is put in your saved searches that you do not enjoy either unprotected sex, bareback and hardsports. This means no profile will come up in your results offering any of them. You would then avoid a good load of the PG scammers and nasty romanians doing this.