Since it would contain the location of the root directory, putting there would be circular. Hopefully the organization has a central location for their documentation that is somewhat organized (via SharePoint, or even a network share with folders). Reducing the number of things that a new hire would need to "just know" to a minimum should be a goal.
> Hopefully the organization has a central location for their documentation that is somewhat organized...
My office uses a combination of Redmine, Slack, email, gitlab, network drives, google docs, dropbox, some pdfs floating around, and a readme in the root of each repo...
Exactly. Because...
It started out on...
That Novell drive
... but then...
That Win95 share
... Samba
... Wiki
... Sharepoint
... nah, let's start using Confluence now
etc.
Thus, the use of README in the root directory of a project.