When you're editing, you're putting it together in a way that makes sense metaphysically. You're not inventing it, but you're finding the story that's there. You're making a play that's eventually going to go on stage and present itself to an audience. You want to show what happened, not exactly what you have evidence of happening.
If you're filming somebody doing something they really want to do, you're probably not very high on their list of problems to deal with. You see James Carville on the phone - he's like that whether you have a camera or not. He isn't doing it just for you, and that's hard to explain.