I took a brief course in accounting. The instructor was a former used car salesman. So we were talking about that business, and he said that the dealership didn't make money off of the cars, they made money off of the financing. And they made that money because the customers simply could not understand interest rates and payments. He said he'd repeatedly patiently explain the options to them, how the higher payment plan would save them money in aggregate. They'd eye him suspiciously, tell him they weren't going to be taken in by shenanigans, and always pick the lowest monthly payment plan, which was always the costliest to them.

This is what happens when you dog learning arithmetic in school, wondering what use it possibly can be. Not understanding arithmetic will cost you real money, a lot of it, throughout your life.