Because a ton of wealth is caught up in assets that were already taxed in some way, or is not directly usable. Yeah I might have a few million dollars in assets, but if those are all caught up in shares of a company I'd have to sell a ton just for the mere fact of me owning them.

I'm personally not at all a fan of double-dipping on taxes. I was taxed to make money and taxed to buy stocks, that should be it until I've sold them or realized any gain from them. Property tax makes sense on some level, since you're taking up physical space and helping to pay for the utilities you use in your area. But I don't agree on a tax for just owning something otherwise, it feels incredibly scummy.

There are other solutions to the problem that don't involve losing shares in a company you've built yourself and still taxes in a way that's less shitty. The rich pay less in taxes by taking out loans against their assets, which is fine, but those loans aren't counted as income for good reason (otherwise buying a house would mean tens of thousands in taxes just for getting the loan), but they need an income to pay back those loans and that income would be taxed, so I'm not certain there's a lot that could be rightly done there, either. It would also fuck with a lot of business financials if you start progressively taxing larger loans as income, but it's something to consider I guess.

I'm not sure what the solution is. Personally I see little difference in someone having 200 million in assets and 70 billion purely from the standpoint of "how much could a person reasonably spend in a year," but I digress.

In my opinion, the more egregious issue is that the mere fact of having that much money could be easily used to manipulate markets and should be considered anti-competitive from its mere existence. Good on you for making that much money, I applaud you, but capitalism requires healthy competition and if you have literal trillions to outcompete competition by hemorrhaging money through losses for hundreds of years then that's fundamentally anti-competitive because nobody's going to challenge you. It's a losing game and breaks the capitalistic contract necessary for a healthy economy.

Companies should not have any means of becoming so unfathomably large, and that alone would resolve the issue of "paying their fair share."