>but hard to sell to merchants, since the merchant pays fees.
There is a nice article which hopefully somebody can link that explains that visa was a success because merchants reduced their costs, too. They had to do informal credit accounting for all their clients who only paid for the purchased goods once a month. With visa, that accounting position, which could be a full-time employee, wasn't needed any more. Furthermore, they reduced their risk of clients defaulting on those micro loans.
There is a nice article which hopefully somebody can link that explains that visa was a success because merchants reduced their costs, too. They had to do informal credit accounting for all their clients who only paid for the purchased goods once a month. With visa, that accounting position, which could be a full-time employee, wasn't needed any more. Furthermore, they reduced their risk of clients defaulting on those micro loans.