One of the huge faults in Bethesda games is that they dont allow you to do "Anything", even though it is an open world RPG. An example would be that you cant kill people who are "Important" to the story line or other quests.
Because it'd be game-breaking?
I mean you could potentially surround a game around a completely choice-oriented story line, but you don't see a lot of games even attempt it. GTA, AC, etc all keep important characters in cut scenes and end the mission if you kill them. Skyrim just doesn't allow you to do stupid stuff with their main-story line, yet they give you tons of choices when it comes to other crap. 
The whole point of an RPG is to develop your character, fight, progress through a story, and usually explore a large world while making choices that can affect the progression of the story. Not to simulate the life of a psychopath.