And I am pretty sure the executives in DFW know a heck of a lot more about their business than you are anyone else trolling around the Internet. If the cargo business was that valuable I am sure they would have kept it. Obviously they felt it was better for the bottom line of the company to forgo that potential ancillary revenue given the long term costs to keep that option open. If cargo were as valuable as make it out to be we wouldn't have seen the long term changes the industry has seen in domestic, over water, and in some cases international flying.
IMO the only reason cargo became a big deal was because 20-30 years 747s, DC10s, and L1011s were the only option for many routes (especially transcons) and they had the empty space to help make those routes some extra cash. FedEx and UPS greatly fill those roles and a heck of a lot more efficiently than a passenger carrier ever could.
But of course, that doesn't fit your narrative so you'll not consider it.
IMO the only reason cargo became a big deal was because 20-30 years 747s, DC10s, and L1011s were the only option for many routes (especially transcons) and they had the empty space to help make those routes some extra cash. FedEx and UPS greatly fill those roles and a heck of a lot more efficiently than a passenger carrier ever could.
But of course, that doesn't fit your narrative so you'll not consider it.