The airlines will always offer an incentive for customers to be "loyal". However, the programs will get smarter, stingier, and more focused. It will become increasingly difficult to game the system. Also, the relative value of these programs changes. The upwardly mobile (pardon the pun) who are early in their careers likely get great value out of them. Those who are further along in a successful career receive less perceived value. Those are actually the customers airlines want to attract so they will offer rewards, sometimes lucrative ones.