A second (simpler?) way is to prevent credit cards from forced bundling of variable fees to the merchant. Credit cards companies are in a very strong oligopoly

A second (simpler?) way is to prevent credit cards from forced bundling of variable fees to the merchant. Credit cards companies are in a very strong oligopoly and are able to essentially demand bundling of all their cards, regardless of the fees charged. If the credit cards companies were forced to charge a single rate for all cards in a bundle, it would allow merchants to either selectively drop higher priced bundles or the card company would have to start balancing the additional cost of higher rewards on their side, moving the incentives back where they belong.