Ironically github is sort of the exception that proves the rule: decentralized in the one way that really matters (decoupled development on individual systems), but centralized for easy interaction in the way the market demands.
But it demands both. The ability to develop in a parallel, decentralized way, and the ability to integrate things at a central point, an authoritative source and a blessed official destination.
It's similar to how databases allow to begin parallel, concurrent, even contradictory transactions, and also guarantee serialized, consistent database state, and rejection of invalid updates, at commit time. Both aspects are utterly important.
So far, having individual small countries seems to keep the centralisation at bay for longer than just having states in a federation.
(Look at Germany, Austria, Australia, the USA for examples of the latter. Interestingly, the UK is legally not made of federal states, but in practice they have granted more autonomy to eg Scotland over the years. And everyone knows that Scotland would secede and get away with it, if there was a power grab by London. In that sense, they are more federal than the US, where secession is very much verboten.)
