This is one of many sleazy bank practices, but one which I was already aware of, which is why I regularly redeem my credit card cash balance before it gets too high.

I think the fact that she lost what was essentially cash makes the bank's offense seem more ... offensive. Some (many?) airlines have a policy that if you don't use your accumulated frequent flyer miles within a certain time period, or if you don't get additional miles within that time, you forfeit all of your miles. People might not know about that policy, and if it gets triggered then that's annoying ... but it would feel even more egregious if instead of miles, you had accumulated an equivalent credit with the airline that could be redeemed for cash.