You're underestimating the value of loyalty as measured by the ratio of trips you choose to take with a particular airline compared to your total number of trips, however many that may be.

In addition, it costs more to reel in a new customer as opposed to retaining one.

ie. I always fly on AA when I can, and specifically I fly transatlantic several times a year. My annual spend isn't huge compared to someone whose business pays for full fare F or J tickets, but since AA's MRTC, and even once it was dropped, I have convinced almost all my family members to travel solely on AA when they have a choice. That loyalty is surely worth a great deal to any airline: they got at least 10 loyal customers because I myself was happy with their FF benefits.

For that reason, I believe measuring loyalty by each person's own expenditure alone is misleading and short-sighted.