Part of the answer is that mortality rates were far higher 150 years ago. A couple might have 5 children but only 2 survive to adulthood.

And if we’re really lucky, the value of TSLA will fall enough that he gets a margin call and is forced to sell shares to pay back the loans.

Ah, but it’s a credit card, emphasis on credit. The bank issuing the card is making a short term loan that will either get paid off by the card holder at the next billing cycle, or will automatically turn into an indefinite length loan at what is usually an exorbitant interest rate.

The bank is always taking a risk that they won’t get paid. That’s why the amount they get paid for this risk needs to scale with the size of the transaction.

Debit card doesn’t have this specific risk; the money is either immediately transferred from the cardholder’s account or the transaction is declined.