My roommate annoyingly locks the door on her way out for work every morning "in case someone comes in to the flat, into [her] room, and steals her stuff" between the time she leaves and when I leave. Our flat is in a locked building. Also I wake up the same time as her and leave 1h later every day. What's annoying is that our door requires a key to be locked or unlocked from either side. The plus side is that it's prevented me from forgetting my keys a couple of times. It sucks when my hands are full of stuff and I'm in a rush to catch the bus