Somebody approached me the other day asking for some assistance with creating documentation for internal procedures and processes. I asked why they wanted to start documenting, and the answer was very interesting.
"I've already been burned twice - I don't want to get burned again."
After some explanation, I learned that on two occasions, key employees had left somewhat hastily - along with them went all of the operational knowledge for doing their job.
Hiring a replacement was almost impossible because nobody knew what the replacement would do - so before anybody could be hired, the individual I was speaking with had to figure it out from scratch... twice.