Making documentation for a changing system is a losing battle, because it's immediately outdated.
The more detailed it is, the sooner it becomes inaccurate.
When people can't easily find what they need, experts like programmers or product managers become overburdened with trivial questions. (Nothing Better than an Expert)
It's frustrating when documents are clearly out of date, and it's even worse when it's mistaken for being accurate.
This struggle to keep everything in sync often leads to giving up on documentation altogether. (Writing is Hard)