The margin on things other than airline tickets is generally much higher than that of air transportation. Selling miles is a high margin business. Selling preferred seats is too. A customer with a co-brand credit card who uses it on the airline’s shopping portal and buys upgrades is a high margin customer, and a customer worth fighting over – and treating well.
This is being recognized by airline frequent flyer programs around the world and it’s time this recognition come to the U.S. too.