I know lots of people who live very nice lives ($300-750k/year spend) using nothing but cash and never showing ID.

There are a million ways to convert it to crypto, and a million ways to convert crypto to many of the other things one might want to use: gift cards, airline miles, etc.

Same goes for gold. There are lots of shops in many countries that will buy gold for cash. Many countries still have hotels that accept cash.

You can pay for a surprising amount of things in cash. One friend of mine simply has a rich buddy buy his cars and insurance, and he gives him paper cash each year for the sum of payments+insurance.

Many landlords are happy to accept cash, especially if you are willing to pay a year in advance.

Why do you think someone with that much money would be driving a car that's titled and plated in their own name?