The article mentions the un-bundling of fees and charges for checked bags,
but doesn't give it enough weight.
As a counterpoint, the author writes, "Southwest Airlines passengers, who can check two bags for free, still seem to fight over limited space in bins."
Assuming that is true,
we're now in an era where passengers are conditioned to carry-on bags.
Changing their behavior solely for Southwest is unlikely, and
also Southwest is a regional carrier,
whose clientele are going to packing for shorter trips,
and thus have less to luggage.
Commercial passenger air transport today is dystopian,
and the small comfort of having your luggage with you to avoid fees, checking bags, and baggage claim,
just to get in and out of the airport as quickly as possible is perfectly rational behavior.