I think it has to do with the corruption at tube sites. Certain lines and stars just get a shit-ton of uploads on the popular tube sites. I really think the average porn consumer goes to one of the top rated tubes and just watches whatever is newest or has the most views. They're not exposed to newbies and unsung starlets. I assume PR and marketing contribute, but I think a lot of it is like... why do people eat Taco Bell- because it's familiar and always there. Oh it must be good cause everybody eats it.