This one falls right under the theory of cards - if a company has a rewards card that can't detriment my credit rating, I'll get it immediately as I double up on the points: first, from my credit card loading the rewards card, and then from the rewards card. DDPerks is by no means spectacular - it roughly evens out to a free coffee per 12-15 depending on what size coffee you purchase. A free coffee upon getting the card is a nice benefit. Additionally, there are some random promotions you'll receive via email for having the card; unexpected point boosts and double point during certain times of the day, etc.
This one is also available as an app, so no need to pack the wallet with another card - although it does mean you'll have to do the annoying move where you try to get the QR code under the scanner.