It's yet another loyalty program so they can track you and your purchases. In return, you get some discounts and digital coupons. I believe they even reserved the purchase of the SNES Classic at one time for Cartwheel users. Look what they're doing with the PS Classic - the stores sell it at full price, even though everyone else has dropped the price to $60, then they make you use the Cartwheel app to get it for $60.