Any number of numerous appliances and hideously malformed business systems that don't have ways to automate cert changes.

Not everyone gets to work in their simple little world of standards-following lab servers.

This has a lot of "I can use the bus perfectly fine for my needs, so we should outlaw cars" energy to it.

There are several systems, like firewalls , switches, routers, proprietary systems and so on that only has a manual process for updating, that can't be easily automated.