Making a film is so hard that if you don't have your main actors going along with the ride with the rest of the crew it can make your life very difficult.
Everyone is sort of in their own little area counting lines and no one talks when film's not rolling. There's constantly actors coming to me back behind the monitor screaming at me, "Why did my line count drop?" It's a nasty tense environment.
People want to see realism in action now. People want the actors to perform than the computers performing. Though I have done both, I enjoy the realism of action more.