Dorothy, I guess your household is the kind Michael Moore famously described as the Canadian norm with respect to door-locking -- i.e., not. Having lived so much of my life in downtown Ottawa, the locked front door is still A Thing with me, although Stratford natives find it a bit, um, shall we say, anally retentive. I just smile sheepishly and say, "Big-city habit" and lock it anyway. In an old house, that way one knows that the door won't accidentally fall or blow open because of a weak latch. In a sketchy neighbourhood, that way one knows that the hung-over neighbour has to knock rather than just wander into the kitchen in search of a Bromo-Seltzer (true story).