That's the only way I can control my movie. If you shoot everything, then everything is liable to end up in the movie. If you have a vision, you don't have to cover every scene.
From a writing point of view, you now have teams of screenwriters working with a director. What's lost in the process is the power of that one heart, brain, gut and soul that makes something an original piece of writing.
But then one day the Lord put us together through our agent and it's been a wonderful match.