You can't use Apple Pay on top of a bank account that doesn't exist. 1.7b of the people in emerging markets don't have access to banking services. 500m+ of them

You can't use Apple Pay on top of a bank account that doesn't exist. 1.7b of the people in emerging markets don't have access to banking services. 500m+ of them have internet/cells and many have Facebook/WhatsApp. Hence Facebook's interest.