There are far too many people too far from retirement age on SSDI.
The largest group is 60-64 years old (about 25%), the two groups below that are also large in terms of numbers ~23% and 17%).
A lot of that demographic was involuntarily retired by the Greater Depression; many co-workers in that age group assume they’d never be hired again if they lost their jobs. Corporate America has no more use for people accustomed to the “before-times” salaries, benefits, and work schedules...