I'd say "users that never use Github, for anything" isn't a very useful measure. It is important because Github has become the yardstick by which everything

I'd say "users that never use Github, for anything" isn't a very useful measure. It is important because Github has become the yardstick by which everything else is measured. People expect git to work roughly like Github. The whole pull request workflow was popularised by Github. Linux and git do not use pull requests. The deprecation of the git:// uri scheme is also Github. The expectation of an integrated bug tracker, comment threads, and wiki is also Github.