Its weird. Stranger is the UFC doesnt feel the need to come out and explain this type of stuff to the public.
I think a real motive here is by reducing/controlling a fighters income outside of the ring, they will in turn force fighters into fighting the fights the UFC ask them to fight and doing what the UFC asks them to do. We won't see as many guys turning down fights anymore if the only way a fighter gets sponsorship money is by stepping into the ring. Fighters won't be able to draw nice paychecks outside of the ring anymore, which my guess is the point.