It is quite common for larger open-source organisations to self-host their repositories and issue trackers. After all, they would quite literally stop existing if Github were to do an oopsie. Voluntarily putting the keys of your entire existence in the hands of a third party isn't exactly an attractive option.
"Literally stop existing"? Having broken links and notifying everyone when a migration happens is for sure a hassle, but migrating a git repo is the easiest thing in the world.
That's kinda the whole point of a distributed VCS.
