Looking a place (look here) shouldn't give you a full description of every minute detail of the room, and it doesn't. The game doesn't calculate angle of view (yet?) either, so entering a room and being able to tell that every door is closed or open isn't realistic either as you most likely can see just the frame on the doors parallel to your facing. Making the doorway visible but not the door itself, you know there is an exit there but no way to know the state until you actually position yourself to see it.(look
Also rooms vary greatly in size, a room can be a tiny bar or a long hallway full of doors. You don't know if all of them are open just by looking at the hallway. You have to actually stop and take some time to check them.
And walking on a closed door is always a good representation of reality. You don't pay attention to things you get surprises.
But a perception check would be cool. A really super perceptive person could tell if a door is open or closed depending on the way light/shadows come across the door's threshold.