Wealth taxes became a big part of American political discourse because your populist politicians realised they can promise voters astoundingly expensive things

Wealth taxes became a big part of American political discourse because your populist politicians realised they can promise voters astoundingly expensive things by framing them as being just a small percentage of the wealth of ultra-wealthy folks like Jeff Bezos. You can't pull off that rhetorical trick by taxing capital gains. Of course, in reality I don't think this would work anyway. All that wealth only exists on paper - it's just the nominal values of their shareholdings at the current market price, and if you make everyone sell at once that price plummets and the illusion disappears. I'm not sure it even makes sense on a fundamental economic level. You can't turn shares in Amazon into healthcare in the way that you could, say, Bezos buying a less fancy yacht. Even though the yacht and the healthcare use different resources, other businesses in the economy with a choice between what resources they use to make their products receive pricing pressure to change that choice and ultimately, it should all sort itself out in the end. That doesn't work here. The only way for the sums to work out is for other people who would actually buy things to forgoe purchases worth as much as whatever you want to fund and buy Amazon shares with them instead - and the whole reason populist politicians want to frame this in terms of wealth in the first place is because what they want to fund is huge compared to the size of the US economy.