Tbf, it only really makes sense for the individual programmer to properly document code if there’s a decent chance they’ll forget (eg some obscure part of the codebase), or if you expect a reasonable chance that someone will have to read the code without you. Otherwise, its useful, but not necessary: you just go to the guru (perhaps yourself); his living body is the documentation.

If you’re thinking that only you’ll ever read it, or you’ll be working on this codebase for the next 30 years, it doesn’t really matter. Peoper Documentation is a cultural activity required for teams, especially those with shifting workers, as is common now. And should really be enforced by the managers, not the programmers thenselves.

Its significantly less necessary when you can expect to spend most of your career on a single codebase, a workstyle these cobol programmers presumably came from.