American Express has expanded its network, making it more attractive for merchants to accept its cards, even if they have to pay higher fees. The result is a snowball effect, where existing customers use their American Express cards more frequently, and prospective customers may make the decision to sign up for a card due to the perks and its widespread acceptance.Top-tier American Express cards come with relatively expensive annual fees, but also some generous perks. American Express attracts affluent cust ...