And of course the many other reasons: convenience, consistency, built-in integration with other development tools...

...none of which requires or justifies the centralization that has been created.

Apparently, many people disagree with you; otherwise, we would not be in this situation.

I agree that centralization is probably not a hard requirement for these properties, but currently no one has come up with decentralized equivalents that provide users what they actually want - and remember, you don't get to tell them what they want!

Why is this not best of both worlds? You have centralized portals like GitHub that have bunch of additional proprietary features, but if you don't need them or don't want to have centralized solution you have freedom to interface with it from, uh, anything.

github does not federate, it is not decentralized and you need an account to interact with the many proprietary features.

You just described https://en.wikipedia.org/wiki/Embrace,_extend,_and_extinguis...