It’s also operationally almost impossible to implement, as what counts as ‘wealth’ is highly ambiguous, and in most cases valuing it even in the best situation is nearly impossible. In a taxation situation even more so because it isn’t changing control between disinterested parties, so there is no one who has the time to really look at and form their own opinion and holding anyone accountable to it on a short timeframe.

A lot of the trump real estate scandals are from him (supposedly) manipulating real estate appraisals for favorable loan and tax purposes, and that is for something with relatively easy/straightforward/understood valuation and an army of appraisers.

Private equity? Partnerships in ongoing concerns? Controlling vs non-controlling interests in various things? Trusts?

There are so many valid ways to look at, account for, and structure these - and they all have wildly different values, levers to change those values, and short or long term valuations and cash flows. If you own a controlling interest in a large business, but don’t sell anything and don’t have income from it (you reinvest it in the business), that may or may not be a lot of wealth. If the business tanks without it, was the business worth anything? Or was it worth something and then it was another factor that killed it? If the business is producing a lot of cash and the owner pulls it out, that is clear measurable income and easy to quantity.

To the point if you threw 5 independent evaluators at any of them you’re probably going to get 7 different actual numbers, all meaningfully different, and all of which could be argued are legitimate.