Recently, AS, UA, DL, and AA have all announced that they are eliminating change fees on domestic U.S. flights. It pretty clearly looks like they had already coordinated this move.
The common theme is that the waived change fees apply only to First Class, Business Class, Premium Economy, and Economy tickets, but not to the special Basic Economy/Saver fare buckets. Naturally, this is good news for passengers booking higher fare classes. But for economy-class travelers, airlines actually still have plenty of room to maneuver: they can simply price standard economy closer to full fare and push everything else into Basic Economy, so they still come out ahead.
One more personal thought on airfare: the more fare tiers there are, and the bigger the differences between them, the more opportunities airlines have to squeeze extra value out of customers through segmentation. U.S. airlines are still world-class at that.
The new change-fee policy applies to all tickets, except for Saver fares. Previously, Alaska's change fee of $125 applied to all non-Saver travel, except for guests traveling on refundable tickets and Mileage Plan top elite status members.