Well, why does something have to be done about this, exactly? Who is getting hurt here? It's not like borrowing is increasing his net worth. Just like anyone else, he has to pay back what he borrows, he immediately owes an equal debt. And that requires actual income, which gets taxed.

Larry has sold tons of Alphabet stock and paid lots of capital gains taxes. This is easily available public information. The whole buy-borrow-die thing is sort of a stupid myth. Actual centibillionaires diversify because the risk of having a huge concentrated position is much greater than the liability of having to pay some capital gains taxes.