My boyfriend NEVER locks his doors, and I mean NEVER, not to his house, his vehicles, nothing. I always lock mine up and whenever I get out of one of his cars I lock the door before I close it. It's the same with the house - I lock the door behind me when I go inside, just as a habit, and he'll later try to go out and ask, "Why's this damned door locked?" I just grew up locking doors, and I guess he didn't, but he acts like I'm so weird for locking everything up?
Do you lock the doors to your house/apartment? What about your car?