Don't knock the Wal-Mart greeters.
I have a neighbor who will turn 80 next week. She works as a greeter two days a week for a few hours a day. Two other days a week, she goes square dancing. She's almost 30 years older than I am and she gets around better than I do. There's a lot to be said about keeping active, even if it's work.
My dad finally got off his retired butt and got a job driving a taxi at the airport in Richmond to suplement his retirement. He was the typical govt slug who retired as soon as he could. My mother retired soon after so that they could travel around the country in an RV. Well, retirement is not great when your only income comes from SS and a state govt pension. My mom still wants new things, now that she sees how well I am doing. The RV adventure finally ended and now they have to deal with their choices of expecting the govt to take care of them.