The conspiracy theorist in me says the following:

Airlines are fully aware that the real cost of supplying award tickets is much higher than $22 each. They report solely the marginal fuel/labor costs only because the SEC made them, and they have are interesting in keeping that published figure down as much as possible.

Why? Because investors may see a frequent flyer liability of $1 billion without realizing that the value of the program through increased sales to frequent flyers is worth a substantial, albeit unreportable, amount. The higher value takes place by paying fares higher than a competitor, booking otherwise marginal trips with the freuqent flyer miles breaking the tie, etc.

I say it's unreportable because I don't think there's a place to put goodwill and that sort of thing on a financial report. Marketing does that, whereas financial reports have to stick to verifiable, "black and white" figures.