I think this is the way they justify their actions to themselves. They get into porn for the money and get to see their selves on tape and they get to thinking. God only knows how that process works but it just may give them hope that their pathetic lives can count for something. Well something more than a place for their daddy to unload his sexual desires.
Holding onto that mainstream dream is probably the only way they can get through the long dark nights. That is until they discover it is not going to happen. Then they trade all those dreams in on a good habit that will carry them until they are shot out in a year or two, so they can move on to the escort trade and further.
But these are just my thoughts. YMMV