the US is in a weird position where the federal government actually has very little power. But it has tax power. So they just use taxes as a way to manipulate things in the way they want.
But as far as I understand, the US tax system is also one of the 2-3 most complicated in the world... Being an permanent resident and not being used to this from my home country, Im making a lot of suboptimal financial decisions purely to avoid complicating my taxes... eg: I avoid consulting like plague, even when I have a worthwhile opportunity to do so.