Not true, there are edge cases. Some billionaires have lived very frugal lives - such as the founder of dollar stores. There was also a multi billionaire who lived middle class and gave away his whole fortune towards end of life

Often that’s image. Warren Buffett enjoys his wealth. He’s just smart enough to know what happens to people who are seen enjoying their wealth, which is that they are despised. Plenty of rich people have one way of living when they are “in the community” and another at of living when they are around each other.

I will concede that you are technically correct, but living a normal life despite having billions is like moving to another country in middle age, not knowing anybody, and not even being able to talk about the place where you’re from. It’s a lot like witness protection, because the moment you tell people about your life before, everything will be different and worse. You can decide to dump all your rich friends to be a schoolteacher in Vermont, but you’re basically changing countries, which is something people rarely do if they have a choice.

The percentage of people who have the courage to leave their reference frame, especially when that reference frame is upper-tier wealth, is just very low.