I think most girls do porn just so they can charge higher rates for hooking, so they can offer the "PSE experience", PSE=pornstar escort. A regular escort might be only to charge $300 an hr but a "pornstar" can charge over 1k.
Bellamodels is a reputable site, not fake profiles. Look at how many known girls are listed
http://bellamodels.com/portfolio.html
Audrey Bitoni
Carmel Moore
Daisy Marie
Jessica Jaymes
Lanny Barbie
Mary Carey
Sarah Blake
Most these girls are charging like $1,800 for sex. It's probably easier for them to hook than do movies because they don't have to fuck for an hour straight or do stuff like dp and hard anal. Of course it's dangerous (supposedly Chole Jones got beat up by a customer once) but I'm sure they all do heavy screening.