The same question can be asked of strippers in every town - why?
Because there is a market for it and money to be made. Depending on the scene and the popularity of the girl, they can make $500 - $1500 a scene - sometimes less, sometimes more. If the market wasn't there, there would be no adult entertainment. If the the Pet Rock still had appeal, it would still be making money for people. Hey, sex sells - always has, and the adult industry profits from it big time. I buy DVD's, so I help pay these girls salaries too. I'm like an unseen boss.