I actually think that a lot of Southwest flyers would be better off on AS (or, at least, they would have been before premium economy)
I think that many of them don't understand same-day changes. I say that they can do a SDC on AS for $25 (intra-CA) and they tell me that it's free on Southwest. I explain that they have to pay the fare difference (and same day tickets are usually expensive) and they tell me that you have to do that on all airlines. Basically, they don't understand SDC.
I'm not sure how an ariline can effectively advertise something like this. People don't like the idea of paying a $25 fee (because fees are "extra") but a $150 fare difference seems "fair" because you're moving to a "more expensive flight".