Trilogies are common in the film industry, particularly in the science fiction, fantasy, action, horror, thriller, and adventure genres.
Under these contracts, actors and actresses were locked into working with a single studio and "were paid a specified weekly salary regardless of the success of their movies".
"[1] Under the new system which replaced it after 1955, filmmaking became a "short-term film-by-film arrangement" in which a producer is expected to assemble an entirely new cast and crew for each project, and rent the means of production from contractors only as needed.
All successful directors and producers have certain favorite cast and crew members whom they prefer to work with, but that is of no help to the studio if that perfect character actor, costume designer, or music composer is already fully booked.
Compared to the previous system, directors and stars spend a much "larger part of their time negotiating each new film deal.