Yes, most domestic US airlines have eliminated change fees. But as you point out, it's not possible to get your money back and it's not easy to make changes if you don't have an alternative trip in mind. Cancellability is valuable (see hotel bookings), and yet, people over-value the option - sometimes out of laziness, or they forgot, or they go with the original plan. I have difficulty believing airlines would lose very much if they offered full refundability up to about 3 or 4 months in advance, but they would probably get more bookings, most of which would likely not get cancelled.