u/the_rainbowfish reminded me of something that happened in my old job. Disclaimer: This happened to another person, and this is all from what others told me.
I was a maintenance tech in a factory, and one day, I encountered the keys of a machine operator left in one of his machines. I later learned that the operator had quit and left the machine's keys there because the factory had not accepted his resignation.
One of the older maintenance techs told me that the machine operator had given his 2 week notice, but the factory rejected it because they wanted him to stay and train someone since he was the only one that knew how to operate specific machines and none of the other operators didn't. (The machines were very old). However, the factory had not given him a timeline of how long this would take and had not selected or hired anyone to take his place.
The operator stayed for 1 month but was not given anyone to train. He was elderly and tired and just wanted to leave. So one day, he packed up all of his tools and left the machine's keys inserted in the appropriate machine and just left. The supervisor of the floor tried convincing him to come back, but the operator told him he was retiring now and would not be coming back.
The factory then pressured one of the older operators into learning how to work the machines. That man also ended up quitting.