This is true but very limited as well. GitHub isn't used for just git now, it's also an issue tracker, a wiki (yes, those are repos as well, but you don't usual

This is true but very limited as well. GitHub isn't used for just git now, it's also an issue tracker, a wiki (yes, those are repos as well, but you don't usually have them sync'd), Github-only services (e.g. Travis), package managers (e.g. Cocoapods and Crates). There is a lot riding on GitHub that developers use. Hell, even closed-source companies sometimes use empty GitHub repos so they can use Issues for openly available tracking.