We never lock our house when we go out (except when we leave for vacation), but we do lock it up at night when we go to bed. I guess our thought is that we aren't really concerned with anything getting stolen while we are away, but it would be awful if someone came in while we were inside sleeping.I can’t sleep without a deadbolt. However I did grow up In a town where there was truly no reason to lock doors. You have to experience to understand. Keys left in cars etc.
Having lived in very small Kansas towns (1200-1600 pop.) for over 20 years, I agree with your wife. For about half that time, I lived alone and never felt unsafe. Didn't have deadbolts in any of the four homes I lived in during those years.
Two of the three towns were on a major highway to the Southwest. Still was considered odd to lock doors. People even would dash into grocery or post office and leave their car running.
Yes, I really think it depends where you are. Growing up in FL, you always had to lock your house and your car in the driveway. Living on a farm in rural NY, no one locked anything and you would often see cars running with the keys in them. Currently, I have two houses-- one where we live and one that I use as an Airbnb rental in a small city about 30 minutes away. One gets locked and the other does not.