I know fairly smart people who understand calculus but just cannot accept that there is a problem with paying interest on all of their purchases.
They simply do not understand that eliminating high interest debt as soon as possible (or never acquiring it in the first place) is essential to ever having financial security.
Honestly it sometimes feels like the normalizing of financial illiteracy is intentional, although I'm willing to accept that the lenders of high interest debt are just taking advantage of the situation they've found.