If frequent flyer credits at United, Delta, and American are earned based on the price of a ticket rather than the distance flown, why are those credits called miles?
Frequent flyer programs were meant to provide differentiation amongst airlines where none existed. Airline seats are more or less commodity products. Programs create brand loyalty, and get a customer to take a connection rather than a non-stop or wait for a flight 2 hours later instead of flying at the ideal time.