> I'm genuinely baffled by this, why are the tax filing options in the US so fragmented?
Federalism:
* https://en.wikipedia.org/wiki/Federalism
> Here in the UK […]
Not federated:
Federalism:
* https://en.wikipedia.org/wiki/Federalism
> Here in the UK […]
Not federated:
As often with US oddities, the explanation boils down to "the US is big enough to make corruption really attractive and wealthy enough to be able to just ignore it".