Back as a kid, not one of of our neighbours, us as well, lock their front doors, except when no one's home or going on vacation. Once moved out, housemates were locking the doors, so followed their lead.
It's a question of safety of course but what would have changed this habit?
We had friends who had their bicycles stolen whilst they were home. I wouldn’t deadlock myself in, whilst home, but I would ensure the door can’t be unlocked from the outside.