I guess I've never worked for a company that functions properly, then. They must be pretty rare.

Even if absolutely everything is documented there is still the loss of familiarity and comfort working with a given system.

Having perfectly documented processes still might mean that a new engineer could take multiple hours following instructions to do what the person who originally built the system managed off the top of their head in fifteen minutes.

In these advanced and complex spaces loosing an employee and starting someone new is like starting a university degree. Shure, the knowledge exists and you can "just read the books". But that takes a fuckton of time in which the new guy is not productive AND needs someone else time to teach them.

So it's a really big loss.

Oh shit where can I get a job with one those properly functioning companies? Because my job right now I got was because I was able to figure out on the interview what the guy before me was doing and the same thing happened with my previous employer.