This.

The flight credit is great if you are booking something a day or two later. But, otherwise, you are not only making an interest-free loan, but committing yourself to AA. Who knows what the schedule will be a month or 4 later? Could be better and cheaper on DL or UA, but you can't book them with your credit.

This isn't necessarily a good reason to pay the premium for a refundable ticket. But, it makes it worth looking at the pricing to make an informed choice.