The "trap" for most users is they don't pay off the card at the end of the month. If half the people using the cards were paying it off at the end of the month, card companies would not offer cash back anymore. Cash back is mostly there to suck you into the card. These CC companies know most everyone never pays off the balance and they make 20-30% every month off the interest.
It's akin to buying a car. A guy like me who pays cash, isn't going to get the attention of car dealers. They make money on the financing through the lending bank. Dealers want you to finance. Where my cash shines is in private car sales, because few people have the money to buy a car cash, and private sellers know they have to give a really good deal to sell the car, or take a beating on the trade in.
Credit card companies create programs that really only benefit them. Kroger and Walmart are selling memberships to benefit the customer first, but it also benefits them. If you have a membership, where are you likely to buy first from? Memberships create buying loyalty.
