Documentation has limits. It’s not like you come out of med school ready to be a doctor. There’s certain types of knowledge most easily modeled by the search engine in your head. Heck the information may even be written down! But in a multi systems failure which page of documentation from the 18 different involved services do you read to figure out how to bring it back up?
Do you think someone brand new to a team with documentation in hand will be as effective as someone who’s been there a year?