So people using excessive amounts of coupons and/or change at checkouts should be sanctioned as well?
Can you not tell the difference between someone intending to save money (or pay their bill) and intending to slow others down?
You could make the argument that cheaters are trying to "have fun"/"win" as well, albeit in a way that negatively affects others.
I haven't seen excessive coupon use banned, but I actually have seen a store make that person wait until the rest of the shoppers cleared the line. Very satisfying.