In a sense, editing a film is doing the final rewrite. It's the chance to change lines or replace them in a different sequence. An editor is also dealing with time, which is more a concern in the musical arts. Only film and music require that an audience comprehend the details of a work of art over a given period of time.
[About the unexpected success of "Star Wars"] I won an Academy Award for "Star Wars" before I'd even started thinking about winning an Academy Award.