I have a friend who does storyboards, he told me this story.
When he first started out he did a gig on some small syndicated show. flustered that it wasn't a major motion picture, he said to one of the guys he was working on the show with "I can't wait to make it to the big time."
guy said back "look around, this is the big time."
meaning: even some one liners on a small lorenzo lammas b-movie/straight to dvd fare is PAY. pay where you DON'T have to get fucked on film. For better or worse, you are acting in a 'mainstream' movie. May never break the box office, but fuck it, you got paid for a hollywood gig.
I saw the check from the Born to be a Star movie. wasn't a boy/girl rate but it was a nice pay day for sitting in a hot tub for an hour.
and of course any one that has taken a dick on screen has no chance to being "next big Hollywood star." but then again how many people have even THAT opportunity? who have NOT had sex on screen.
Realistically getting paid to NOT have sex on screen on a continually basis, isn't bad bread.
Also take into account joining SAG gets her union rates (which are pretty much double non-union, AND SAG has very good medical and dental.
SO aside from the arms crossed, smug internet guy posts, what is the downside?