I think for similar reasons that backups and regular server maintenance languishes: "it's working, I don't need to do anything." until something goes wrong. Then they're multiple versions out of date, or have no backup, or have half their VM's showing awful performance then wonder where things went wrong.
Apathetic engineers is often the problem. Just as often, though, they aren't given the people, tools, or budget.
Non tech companies see tech refresh and upkeep as a pool from which to steal people or dollars for other stuff. Until something breaks in a way that it hurts the business.
