Apple Pay will have support from all of the major US credit card companies as of this fall, when Discover begins allowing its cardholders to use the new mobile payments service. The service launched in October with support from Visa, MasterCard, and American Express, while Discover remained conspicuously absent. Since then, Apple has continued to add banking partners so that more people can use Apple Pay, and today's announcement should open the service up to yet a larger market. It's not clear why it took Discover so long to sign on. Though Apple supposedly receives a small cut of every purchase, Apple's mobile payments service is one of the few that isn't trying to cut out credit cards altogether, so it's generally been seen as beneficial for credit card companies to sign on.