The market is segmented reasonably. Most people won't pay for business, so most seats are economy. On certain routes, the flight is so unpleasant that economy w

The market is segmented reasonably. Most people won't pay for business, so most seats are economy. On certain routes, the flight is so unpleasant that economy would be unbearable for most, so airlines have planes that don't have economy (e.g. SIN-JFK on Singapore Airlines used to be all business class; when the route comes back with their A350-10 deliveries, it'll be all premium economy and business). Personally, I fly only in business or first on long flights, and buy economy on short flights. It's worth it to me to avoid the jet lag and be able to bear the amount of travel I do (in the past year I've probably done over 40 flights >5h and close to 100 flights total). Flying domestically in economy becomes a lot more comfortable if you give a legacy airline your loyalty. e.g. I get upgraded to first two third of the time and always get the best seating, priority lines, free drinks & food onboard, and lounge access as a United 1K frequent flyer.