Right, and that's what I was trying to get at when I mentioned that "some portion of the miles will expire or never be redeemed", but I guess it should be emphasized since it's the main benefit to the carriers.
If you have a Delta credit card and you never redeem the miles, the rational thing for you to do would be to switch to a credit card with a different rewards program.
The reason you'd keep using your Delta credit card is because you anticipate that you will redeem the miles for air travel later. The value of the miles still ultimately derives from their "flying business".
If you have a Delta credit card and you never redeem the miles, the rational thing for you to do would be to switch to a credit card with a different rewards program.
The reason you'd keep using your Delta credit card is because you anticipate that you will redeem the miles for air travel later. The value of the miles still ultimately derives from their "flying business".