You’d be surprised. I had some security devices that I was actively using get shut down simply because some paperwork didn’t get filled out properly and the data center team claimed they had no documentation on them.

company a gets bought by company b. company b fires 50% of company a.

even a scream test won’t get you answers because nobody is around that could complain nor know where the docs are.

You’d be surprised with inheriting tech debt. Quite often there’s no documentation, the last person to log in to the system is an admin that quit 3 years ago, but it doesn’t much matter because that’s only for a direct console login which normal users don’t do when accessing the application. With tribal knowledge gone and no documentation, only when you pull the network for a bit do you discover that there was this one random script running on it that was responsible for loading up all the needed data in the current system, when 9 of the other 10 times those scripts were no longer needed.

In a perfect world you’d have documentation, architecture and data flow diagrams for everything, but “ain’t nobody got time for that” and it doesn’t happen.