Re: Amazing (in a bad way)
Mind you in some countries for most people there's very little they need to tell the taxman. In the UK most people have nothing useful to tell HMRC. If you're not a contractor then about the only thing worth reporting is payments into a private pension if you are a higher rate tax payer. That's about the only thing that can reduce your tax bill. And even then, after a couple of years HMRC sent me a cut down form and just asked for that information and any savings.
These days it's unlikely they care about savings because of the allowance and low interest rates. So I bet for over 90% of the UK workforce PAYE is all that matters and that's automatic.
Of course that doesn't mean we have a simple tax system. Gawd no. More likely it means that the system has evolved to the point where nothing the serfs do matters and it's better to keep them in the dark about how the government fleeces them :-/