More like they are their own profit center, they generate this massive revenue selling miles via CC signups and other cobrand activities. I'm guessing they figure they they can have their cake and eat it too, ie extract more profit from the miles side of things, after all the average customer is happy if they can book DEN-DFW for 25K miles each way. This may work but they also risk losing a segment who pay attention. They may find they are not retaining some long time customers.