Also change of aircraft utilization and cofiguration. BOS-LAX used to have a daily three-class service with dozens of premium seats (9 P, 30J as I recall) as well as 2 752s (22 F seats). That's a total of 83 premium seats per day.

Now we have only a few 738s at 16F seats each. Not nearly enough premium seats for the citypair.

So this is a market where at least F cabin fliers might arguably be better off with the 752 rather than the 738. Inferior seats, some folks think, but more of them. Also the nice mid-cabin lav to keep the coach pax out of the F lav.