A lot of wealth is generated via investments which can be reinvested without ever paying capital gains tax. I remember reading somewhere that a dude who had $50 million simply lived off his yearly dividends which was like $800k a year or something crazy. So that's what was taxed....not the massive amount of wealth he had sitting in his accounts.
Honestly even greater than this problem I think are the corporate tax loopholes. You have corporations literally paying NO tax on BILLIONS in profit.
The problem with this is if we start taxing the corporations the way they should be they'll move their operations overseas, you'd have to literally threaten that they couldn't even sell their products here if they didn't adhere to the tax laws.