One reason is that the intensely wealthy class doesn't simply spend their fortunes on more food or more sheds to store more lawnmowers or extra rice cookers or patronize more local businesses across the country. They might buy more beds for their now larger mansions, but their rate of consumption doesn't scale linearly with their wealth beyond the median. I seriously doubt they're commonly buying even 12 to 20 yachts, and if they buy 45 cars they aren't driving them enough to also be buying 45 times the maintenance since you can't drive more than one car at once.

Instead they invest their fortunes into private equity and other capital like homes that, after driving the cost upwards, will now rent to the people who are, economically speaking, incomprehensibly far beneath them. They will acquire hospitals, doctor's practices, homes, drug rehab facilities, banking institutions, water utilities and electrical companies to fuel their own wealth. They squeeze out the stakeholder in preference for shareholders who will demand stock buybacks to provide additional returns on investment.

The result is that the people who are on the losing end of wealth inequality will have no voice in how the resources are deployed, the cost of the utility provided, or the capital to compete in the market. It drives the cost of inelastic supply upwards as its utility is no longer a home but an investment vehicle. Generational wealth like farms become corporations which pay their profits to someone other than their local community. National banks squeeze out local institutions with stake in their local economies, they will burn cash to buy the market out from local economies and the profits of life vanish from the people who live it. When there is nothing left to buy, they'll buy the government.

UBI, GMI are bandages for gaping wounds.

I agree. The arguments for UBI can’t be economic because it isn’t economy. The arguments have to be democratic. This also sustains why it must be federal or perhaps at the state level, versus municipal.