Name change because this may well be actually outing.
I live on an estate which is flats surrounded by privately owned houses.
The flats have security doors, plenty of CCTV cameras and good secure front doors.
This did not stop a locally well known "harmless" homeless man following a pensioner home and murdering him after observing him collecting his pension. They arrested him and he is due for trial but the pensioner is dead from what the police spokesperson termed blunt force trauma.
Before anyone takes issue with my description of the alleged perpetrator, it's on CCTV, that's how he got caught. My point being this, you cannot trust someone will not harm you just because you are used to seeing their face about locally and are not perceived as a threat. Nobody knows what goes on in the mind of others.
So, too right, I keep my door locked.
I have had my locked and bolted up front door handle rattled by people trying it on dozens of time in my thirty years of adulting.
Again, keeping that bugger locked.
A nod to the thread inspiration, no way on this earth would I go for what I knew was going to be an uncontrollable diarrhoea and vomiting trip to the toilet with the door unlocked.
To those saying, leave it open, what are the odds a nefarious person is walking by at that moment. A little story from my youth. 1am, walking with a group of friends and acquaintances through a nice housing estate. One house had a small bunch of keys left in the front door. One male acquaintance spots this, sneaks up to the door, quietly locks it a walks off with the keys. I thought he was going to take them back next day but later was told he'd given to keys to an older relative who went and robbed the place blind, splitting the proceeds. Is one of these reasons I don't trust people or chance.