Came out of retirement and went back to work. Lots of different reasons and circumstances to do that. I used to work with a guy who was a retired aeronautic engineer. Had saved up plenty, financially didn't have to work. He was in his 70s, worked part time retail. Why? "I gotta get away from the wife. I love the woman, but being with her all day every day is too much. And if I'm gonna leave the house for a few hours, might as well do something useful and make some money."