BTW did you know the above are the number 2, 3 & 4 largest software companies in the world respectively[0]? Also I suspect "doing nothing" is a bit of an exaggeration and/or OP isn't 100% privy to what these people actually do. It's probably a relaxed pace but not literally "nothing" & their experience and knowledge still make that valuable for the company.

[0] https://en.wikipedia.org/wiki/List_of_the_largest_software_c...

Politics, knowing where bodies are buried and entrenched bureaucracy can be just as much "tenure" but for staff.

It can be pretty bad, and often is.