Use of cards results in higher prices because they charge merchants for the service.
It's like paying with paypal for everything. When people list items on eBay they set starting prices or reserves with the eBay and the PayPal fees in mind. Some even offer lower prices and prohibit the use of PayPal.
In the real world, the credit card fees are currently absorbed into the increased prices you gladly pay.
20 or so years ago, you could find many lower priced retailers who refused to accept credit cards because of the fees. ARCO gas stations were much lower priced in So Cal when they did this and before they were merged with BP.
So with Discover, you are enticed to use the card with the teeny rebate of the higher prices you are now forced to pay for everything. The card folks are getting a MUCH better rebate than you are.
Think of taxes and tax refunds. Is the government "giving" you money when you get a refund, or are you simply lending them the money all year with zero interest?
This still does not address the issue of pointing at the picture on the card and shouting "HEY LOOK AT MY SPACE SHUTTLE ON MY CARD". The machine at the gas station usually does not react (unless it's related to a component on the STS, in which case it might kvell).
-Fred Shecter