That is a good theory, and in a perfect world you would be right. Unfortunately, Southern California has a lot of people dwelling near these airports. Having controlling facilities helps keep the entropy somewhat contained. Too many varieties of airplanes go in and out of these airports daily and having a skilled professional usher these aircraft in a safe manner makes everyone's lives much better.
Southern California airspace is a challenge, but its manageable with the users making decisions with regard to use of airports and times of operation.