That doesn't seem to be an issue for Bellator. In fact they set up tournaments so Zuffa names will make runs frequently.
More likely, Bellator puts a premium on excitement and marketability from their fighters. That's why they released Bruno Carioca after a win, Aliev after undeserved sd loss, Indio after a questionable sd loss, Machaev after a win, etc. That's also why their interest in retaining Askren is limited, but they fought tooth and nail for Alvarez. And that's why they passed on Volkmann and Fitch, but went after Sass, Etim, and Nunes.
WSOF seems to be more about the sport aspect, Viacom the entertainment.