I would think that AA would appropriately prefer to keep your money rather than give you a cash refund. I think the system is intentional and generous. They will give you a credit or allow you to change your flight without a change fee. (You have to pay the difference in the fare or get a credit for the difference if cheaper) Furthermore, AA will issue a cash refund if they cancel the flight. I have one ticket for Hawaii that I have changed three times. I received a credit for a lower fare twice and had to pay a little extra for the last one.

It does not seem odd to me, especially considering that you purchased a nonrefundable ticket. It would be a poor decision for them to change it to a refundable ticket as you are suggesting. Assuming they do not cancel the flight.