It's not his compulsion, he only does what the script writers say to do. You will notice sometimes on many shows a character seems to do something that is out of character. That is a new writer or a writer on a bad day. Actors only act and seldom go 'Off script.'
Really? The actors have no clout at all? I spent 5 years covering Hollywood as a TV columnist and my experience is very different. Writers are the lowest people on the totem pole. Most character development in series TV results from interplay between actor and director. Writers do as they're told, with rush overnightor on-the-spot script changes when needed.