Offshore bank accounts.

Someone arguing that rich people hoard their wealth brought up the dreaded specter of "offshore bank accounts."

So apparently offshore bank accounts are like Gringotts, where the piles of gold coins just stay in the vault.* Nobody, I guess, borrows money from offshore banks? So why do those greedy rich people willingly forgo the opportunity to grow their wealth further by loaning out their money for interest?

*Now that Rowling is a billionaire, does she have a better understanding of banking, or does she cash all her royalty checks, buy gold, and keep the gold in a vault?

Think of J. K. Rowling, for example. Her conception of a bank when she was a poor person writing her first novel was that all the money was literally sitting in personal vaults, and people went to their own vault to get some of their own money out when they needed it.