Before 401K, large private companies provided pension for retirement. At the time of retirement, the retiree usually choose to have annuity (regular payment until death) or lump-sump. Most people choose lump-sump, because death would ends annuity and children won't get anything, unlike lump-sum.
I suspect this is why the old gentleman kept working, because his divorce decree said if he got his pension (either annuity or lump-sum), he had to give a portion to his ex-wife (maybe 1%, maybe more, depends on their circumstances)
This kind of pension is very rare now. With 401K the division is easier.
To read more about old-time pension system, see https://www.pbgc.gov/about It is not just government employees. PBGC is a government insurance agency for private pension, like FDIC for banks.
