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.

Indeed. We have a top capital gains rate of 23.8%, a top dividend tax rate of 28.6%, and a top earned income tax rate of 40.6%. I can't think of any good reason capital gains should be taxed at a lower rate than earned income.

If you want a wealth tax, without the overhead of having to value all of your property every year, repeatedly forcing sales of illiquid assets, the easiest way to do it is the estate tax, which you only have to pay once in your life. This has also been gutted, and now a married couple has to have an estate of over $22 million to be subject to it at all.

We really don't need any new types of taxes, we just need to put fair rates on the ones we already have.

I was disappointed to recently learn that Canada also has capital gain tax loophole weirdness - up here income from capital gains is counted half, so if you make 75k in salary and get a 50k payout from options when your company is acquired then you're taxed as if you made 100k... there is no distinction for capital gains from primary property ownership or any other limitations, all capital gains at 50%.

Because wealth taxes are harder to implement than income taxes while being economically isomorphic to them. The great triumph of financialization is establishing a clear equivalence between present value and future cash flows, so taxing one vs the other is tomato tomato.