Originally Posted by Fuller.CM

According to the google double click ad planner...

Pornhub: 8-10 million daily unique visitors
Xvideos: 6+ million daily unique visitors
Xhamster: 6+ million daily unique visitors

Like any good business, the producers go where the eyeballs (and their most likely customers) are. So to answer your question, this is why producers work with the tube sites. From our experience the relationship is actually friendly between all involved once the producer knows their content can't appear unless it is authorized.