I understand that the fees from credit cards, etc. are a significant potential source of revenue, but the airlines have diluted a prime purpose of loyalty programs.
Because the benefits of membership dropped and free trips became more difficult to schedule, I just started flying whoever got me there the the quickest and least expensively (or combination of the two).
There is no real point in accumulating mileage and quite honestly; the inflight service is typically equally poor on most airlines.