Yea, GMs open doors. This is not a computer RPG it is a tool. Just like any tool, you have to use it the "right" way. Sure, I agree that it would be cool to allow players to open doors, but the reality is that it just simply isn't worth the time and energy to "fix" something that isn't really broken. GMs should always have the ultimate control over the game and that means the map as well. Visibility within the room is easily controlled by leaving the existing VBL in place, opening the door, drawing a new VBL line over the door and erasing the part that is "open". However, once VBL can be attached to symbols then that process will go away and will behave like you said, but the GM will still be opening the doors.