Tell me, how do you search and collaborate on code that's fully distributed (in the git sense)?
Nothing stops you from publishing the same project to both github and gitlab.
Why would a project that's already happily working with the Github ecosystem want to also have to support publishing to a platform that doesn't block China? Lots more work on project maintainers.
Yes, that's very much my point - GitHub is.
To suggest that GitHub is somehow the same thing as git, but centralized (=> bad) is missing 99% of the value GitHub offers.