That would make too much sense - incentivize customers to use unsold inventory before it spoils.

Instead the greed factor trumps all - airlines believe that you would use a last minute award instead of paying for unrestricted economy. In fact most business travelers don't use awards and most leisure travelers would be loathe to pay these fares, so the revenue that would be lost from last minute awards is mythical.

As a practical matter, this would benefit students, retirees and seniors but not too many others as most of us need to plan vacations months in advance and can't take off on the drop of a dime. I'd much rather see transparency in FF award inventory release dates and available seats.