Shrug
Nothing prevents usage of GH in a decentralized fashion. There's nothing magical about git remotes. Just add some more, figure out a process that works for you, have fun!
In reality: when I want to send a letter I don't want to figure out a process from scratch. I want to go to the local post office, buy a stamp, and post a letter.
Convenience is a spectrum and different people land in different spots. What irks me is when I lack the choice. And that's not the case here.
> Nothing prevents usage of GH in a decentralized fashion.
Do you mean Git, not Github? Because Github is centralized by definition, “using it in a decentralized fashion” doesn’t make sense.