Originally Posted by
Jeffrey Paul
I'll keep the Delta reserve card for the annual first class companion ticket but as far as actually using the card why would anyone do that when you can earn more points/miles, and more flexible points, by using the Amex Platinum card?
Running money on a Delta branded Amex (particularly the Reserve) accrues status. For example, in the current year, $280,000 of charges would earn Diamond outright with no other activity. In past years, it accrued some MQM and waived the MQD requirement.
In practice, most people probably do it out of blind loyalty, but if you're looking for a game theoretic reason that's it.