That sounds like a joke, but that's exactly the problem: the VCS has been distributed, but not all the services enmeshed around it: all the discussions (issues, pull requests, design debates, …).
Github makes it easy to host git repositories, but so do a bunch of other services and it's not that hard to host your own either way or to set up trees of repository or multiple mirrors or what have you. The reason people use a central hub is all the meta-information and exchange about the code and the contributor communities.
The repository on its own has very little value.
And lest you think it's different for the kernel or whatever, a mailing list or an IRC channel are still centralised SPOF[0], when the ML provider goes down so does the project.
[0] though possibly more resilient and easier to switch out of ones