We didn't lock our doors for 32 years. For 20 of them, we lived in a very safe town. Zero crime anywhere near where we lived. For 12 of them, we lived in the country, which turned out to be a very safe place, once I got over my fear of serial killers lurking in the woods. I read too many thrillers.
Now that my daughter and I live in town, I do keep the doors locked even though this turned out to be an area of town that is pretty darned safe. My dog is the type who will show illegal entrants the way to the good silver (not that I have any, but he's not picky about his labels). And the bat and cast iron skillet won't work to protect me if a stranger does enter my home because I am too weak right now..