That doesn't make it any less of a duopoly. The whole point of the article is that visa/mc have too much power and there is a lot of systemic risk by having only two competitors in this industry in particular.
Even if they aren't extending credit they're still facilitating the transaction - it's not like the visa sticker is on there for marketing purposes
Even if they aren't extending credit they're still facilitating the transaction - it's not like the visa sticker is on there for marketing purposes