Free source code hosting.
Years ago, I was trying to decide between Subversion, Mercurial, and Git. I liked Mercurial because it was written in Python. I created a Mercurial code hosting account at Bitbucket.
Git won the version control wars. Subversion is now considered evil by the cool kids, and you don’t hear much about Mercurial any more.
Bitbucket used to be only Mercurial – but they added Git several years ago.
By NOT having my source code hosted at GitHub makes me special.