When they're working, they're regularly talking to people outside their comfort zone about potentially challenging questions. That gets largely shutdown once you retire.
Both my parents were in a huge rush to retire early, and now they just sit at home and scroll Facebook. I don't see the appeal.
Leaning into stereotypes, the older women in my family did just fine in retirement because they just started doing social activities full time. If anything they retired and got busier. The older men sometimes did ok but usually did worse.
And super true for those parents, my goal is to travel massively as much as my budget and health will allow it. Backpacking all around south east asia, thats what keeps me pushing to work on earlier retirement. Sitting at home unless forced, no thank you thats a downward spiral
My retirement plans look somewhat similar to how Knuth spends his time. Long hours of deep intellectually challenging work. Driving long distances and eating tasty food some where far away.
Most of retirement motivation comes from feeling the sun during weekdays. There is little point to be sitting whole day at home.
This is characteristic of acedia.