Has there ever been a burglary or assault from someone keeping an old key and using it on new owners?

Question

It's "common knowledge" that you should change keys on move-in. Usually this is suggested to avoid burglary (or for Googlers and more casual conversation, "robbery"). But has anyone actually used an old key to break in somewhere? You'd think with this being such a common fear that there would be at least one documented case.

Assuming other people lived in this space before you, it’s worth changing the locks on all of the exterior doors before you move your stuff in.
— New York Times, Feb. 25, 2020

The previous homeowner’s friends and family could have copies of your home’s keys, so call a locksmith and have all the outside door locks changed. Also, change the garage door opener codes.
— 10 Tips for Settling Into Your New Home

When you move into a new home, you should change the locks on your house. You have no idea how many copies of the house keys are floating around out there from the previous homeowners, so changing the locks will keep your new house more secure. Tom recommends changing the locks whenever a new home is purchased.
— Changing Locks on a New Home

Some fears seem particularly unfounded:

1. The old owner/tenant will come back and steal stuff. There are people who would steal when they have the key, but not when they could pick a lock? And with them being a key suspect? In the case of tenants, plenty of tenants have access to mailrooms with possibly lower-risk theft available.
2. Contractors will steal stuff. Not only would this be unlikely to work, contractors are around high-value items all the time. You'd think they'd have a more perfect crime, like stealing from an unattended property they are contracted on, or inflating quotes. If caught, they risk jail time and little hope of doing more contracting after going through the legal system.

[Sexual] assault fears are more logical, because you can't assault someone in an empty mailroom or on a vacant property. That is, you need a "someone" to assault someone.

The closest I could find is a master key for an apartment complex, but that's not quite the same.

It's cheap enough to rekey or change locks that it's not a huge concern, but I'm wondering if there's any truth to this wisdom.

For partial credit, do home insurance companies have anything to say about changing locks? The closest I could find is requiring evidence of forced entry for a burglary claim. If rekeying reduced burglary, you'd think insurance companies would offer a discount for doing it.

Sure, unlocking a door won't be forced entry, but that doesn't mean it actually happens with old keys. Especially in the face of what one possibly fear-mongering ABC piece calls easily accessible bump-keys.

Answer 1

Sure, it happens.

The deputies responded to a call of the alleged robbery just before 9:20 p.m. at a home in the 10500 block of Hemlock Avenue and learned that three men entered a home using a key belonging to Joshua Anderson, 26, who used to live there, according to a San Bernardino County Sheriff’s Department news release.
— Two Hesperia white supremacists arrested for home robbery

Here's another example, if you believe the court records:

According to court records, Jeffrey Jorgensen, the man charged in the burglaries, got a key from a resident after an August 1996 date, then returned several months later -- after his date had moved out and a new resident had moved in -- and used the key.
— Apartment residents wary after lingerie is stolen 200 undergarments taken in year, police say

And another:

At around 11:45 a.m. on Friday, a 33-year-old woman was slapped and threatened by a woman who used “an old key” to get into her home in the 6300 block of Ransom Street, in the Pines Village neighborhood of eastern New Orleans.
— Woman enters former apartment with key, gets violent

I also found some stories where an estranged son or ex boyfriend was the one breaking in. If you're willing to accept stories backed only by Reddit upvotes, then the old lady next door may break in too (though her crime was watering the plants).

I do agree that it seems like an unlikely, high-risk method of entry. You'd probably find a lot more examples of criminals getting in via other methods.