Simply because flying passengers is a losing business.
The ones that make money operate as financial services from selling points to their partners via their frequent flyer programs.
The ones that make money operate as financial services from selling points to their partners via their frequent flyer programs.
Consumers compare prices and will always take the cheapest one, even if it's only by a few dollars. They don't think about which airline would be more comfortable, so they make comfort worse and worse. There's very little room in the market for a less-uncomfortable plane. They can auction off exit row seats, but for the most part it's "cattle car" and "first class" at ten times the price (for the people who don't care about price at all).
Frequent flier programs try to stem the flow of people to the cheapest airline, but it doesn't help all that much. They get to charge slightly more than they would otherwise, especially since everybody has a frequent flier program (so everybody gets to raise prices and nobody gives you the even-cheaper alternative). But the various benefits that they use to entice you eat up most of the profits.
Basically they're hoist by their own petard. They promised lower prices but didn't think they'd have to deliver. Instead consumers took them up on it, in droves.
rising cost bases in legacy fleet costs, engineering costs. a lot of airlines fail near their capital renewal programs as fleet age > 25yrs
pure domestic competition beomes a race to the bottom between full service and low cost carriers removing any premium