GitHub and BitBucket are proprietary web applications. This makes them unfit for hosting Emacs.
Also, the pull request system is not very good, IMO. It encourages bad practices like having to use git push --force to submit a new patch set without opening a brand new pull request (I suppose you could delete the remote branch and recreate it each time). And then there's the merge commit that it adds if you merge via Github, rather than rebasing to master and doing a fast-forward for a clean history. As ugly as it is, I much prefer submitting a patch set to a mailing list.
And on top of that, "github issues" are missing core functionality, such as attaching files.
When RMS allows Emacs development to be hosted on Github, Hell will freeze over and the Cubs will win the World Series.
It's a pity Github has become the central place for people to host free software while not being free itself.
And he does have a point. I for one do not look kindly on projects that still use Google Code or SourceForge for hosting or other version control systems other than Git or at least Mercurial. And this is because I look out for projects that aren't well maintained - after all, the noise amongst open-source stuff is incredible and I take notice of things such as when the last release or last commit was, current issues, mailing list activity and yes, the tools used.
That said, it's a pity that Emacs isn't being hosted on GitHub or BitBucket, because if these services are good at something, that's quick browsing of recent activity, plus they provide pull requests.
https://lists.gnu.org/archive/html/emacs-devel/2014-01/msg00...