Why do people buy what they buy? Many marketers assume that buying decisions are made logically. A prospect for a service adds up the cost and benefits of one service, compares it to another, and chooses the service with the better score… right?

But seemingly sophisticated prospects for even sophisticated services do not behave this way, as the strange case of Visa versus American Express clearly suggests. Consider the evidence.

Visa cards are accepted in almost 3 times more locations than American Express. You can pay back Visa immediately, or over time. You must pay on an American Express card at the end of each month or suffer substantial penalties. You pay $20 for a basic Visa card, and $55 for one from American Express.

Now, what truly rational people want from a credit card is utility relative to price. Truly rational people want to pay as little as possible for credit card benefits. A truly rational person, in other words, chooses a Visa card. Maybe all of Earth’s rational people do choose Visa, but that leaves 25 million+ Americans who use American Express cards. Why?

Because of prestige, apparently. This is to say, American Express emphasizes that “Membership has it’s rewards.”

“What’s the point?” you might ask

Appeal only to reason for your prospects, and you may have no appeal at all.