The revenue-based model with the legacies really devalues loyalty from infrequent flyers (typically vacationers) who fly on low fares and hope someday to get a freebie. That had been a very successful business driver for so many years, and one that Delta used in fighting ValuJet and others back in the 90s. But now that we're down to just 3 legacies (and WN) the competition isn't what it was and the big airlines have been more interested in revenue gain. They'll find a much more depleted base to try to lean on after the next black swan event, and the biz travelers who are still loyal (probably from being hub-captive in a lot of cases) probably think they fly enough as it is.

Meanwhile, the minting of miles for credit cards or via other partners continues, so the ratios with unredeemed miles vs seats available could still be bad. Delta is trying to get people used to higher miles required and no award charts, and others aren't much better.

All of it just gives a huge opening to outfits like the Chinese cheapies, the ME3, Wow and others of that ilk, and WN or F9 or NK domestically.

Would also agree with sdsearch that having lots of miles that ultimately never get used is a big part of the assumptions. Though they have to be mum about that.