dbaker assumes (I think mistakenly) that frequent flyers come in only two flavors - always full fare and always discount fare. Although there are some of each, many more FFs fly a broad mix of fares, and no airline will ever get a full fare out of someone they treat like crap when they buy a discount fare. Simple as that. That is yet another reason the mileage based loyalty schemes developed the way they did.
As an EXP, AA treats me like royalty no matter what my fare is that day.
FFs will not stand for the "what have you done for me TODAY?" treatment; FFs want to be recognized for their annual contributions to their preferred airline.