Amazingly, porn attracts the lazy and the criminal as well as the slutty and vacuous. I know. Who'd a thunk it? So for every honest, decent hard worker in any area of the biz, there'll be 10 thieves in the background at every single level (from mismanaged accounts down to infected talent masking by self-medicating, for instance).
Since most of the girls are competing with each other, bitchiness ensues. Since most of the male talent wants most of the girls falling in love with them (and demanding to work with them) and not their rivals, chest-beating ensues. Since most of the producers are competing with each other, back stabbing ensues.
When a member of one of those tribes is pissed at another one, theft seems to be the easy way to get back at them. It's easy, it's anonymous and it generally doesn't lead to physical confrontation, just emotional grief for the victim, which is what the thief wants, more often than not.
You have to remember that a massive number of the people in the industry are not fully emotionally developed. They act like kids and behave like kids because, emotionally, they are kids.
And did I mention