It's a risk to the banks.
If you buy bitcoin with a credit card, but don't pay it--The bank won't get the newly printed money back since they can't get it without your keys.
Discussion
its always a problem to use credit.... but if i would be able to get a 100B USD credit, i would take it, buy bitcoin, divorce, then default and let my ex support me for the 10y's. after 10 years it aged enough so the bank cant get anything back. :-)