America doesn't really have people who've been billionaires for 7 generations.
But America does have people who were born into enough money to never have to worry about finances ever, had children with the same benefit, and had grandchildren in similar circumstances. Plenty of people in politics are the son or grandson of a line of rich politicians. Plenty of comfortable millionaires got their start from a lineage of inherited wealth.
It's not enough money to rank on Forbes 400 and build private castles that'll last centuries, but it's definitely wealth and status being passed down. It's safe money. Many people who became billionaires aren't there through safe, steady, risk-free financial management.
Even if you ignored inflation, how much cash would someone have to accumulate in order to sustain a middle-class lifestyle for their family for multiple generations, if they weren’t investing and managing those investments?
- Marrying well i.e. marrying smart and successful people so that your progeny’s genes are the best they can be.
The British aristocracy was famous for doing this. Marrying old blood to new blood. However, many cultures do the same. That is why marriage was so often a negotiated affair.
His argument is that dynastic wealth doesn’t persist in the United States. If it did, then wealth would STILL have accreted to renters even if most of the wealth was created since the 50s.
Furthermore you didn’t bother reading or noticing that he is in favor of an estate tax.