Actually I've had occasions where people want to see the card (usually when my Secure ID isn't on the ticket, so I don't get Pre-Check; the check-in agent has to add to my ticket); it's just much easier to hand over the card than to argue that it's not required (since it does show it online in the approval letter).

Anyways even though I didn't get one from the get go, I applied and get one in the mail very quickly.