Who would want to be an extra then? Aren't most extras people who want to break into the film business? If you are an extra for one movie and the studio owns your likeness forever, how will you get another job as an extra or a cast member? They wouldn't need you since they already have your likeness to use as they please in any film they want. I mean owning the your image within the movie is understandable. But owning your likeness which is transferable across films and mediums is rather amazing. I can't imagine extras are paid that much to begin with that it'll be worth it to sell their likeness for one days pay.