Those who pay the fees (merchants) aren't the ones who chose which cards their customers have. High fees also seem to allow high rewards to draw more consumers.

Those who pay the fees (merchants) aren't the ones who chose which cards their customers have. High fees also seem to allow high rewards to draw more consumers. I think it would be difficult to challenge Visa and MC just by undercutting them. It seems that regulatory action is the most likely thing to break Visa and MC's dominance.