That’s security through obscurity, as well as shared keys.

What happens when the burglar in waiting watches someone grab the key and use it?

Or in the case of phone security, what happens when your address is printed on the key?

A better analogy is fire lock boxes, where apartment complexes have a master key stored in a box out front that can be unlocked with a master key firemen carry.

Unfortunately, that bic pen trick turned out to work on those lock boxes a decade or so ago, meaning all a burglar needed to get into ANY residence in ANY building with a fire lock box was a bic pen. In fact, a burglar could open the box, get the key, duplicate it, put it back in the box, and nobody would even know security had been compromised.

It’s a pretty good analogy for what’s being asked for here.