Part of the reason for the slow adoption is that from a user experience point of view, there isn't a strong value proposition for the shopper to use Apple Pay. Paying with a credit card is just as easy, and usually a bit faster.

The real shopper pain is with online payments. If you are not shopping at Amazon, and to a lesser extent with Paypal, checking out takes time and is not an enjoyable part of the shopping experience. With a 90% mobile browser abandonment rate, shoppers definitively expressed that they don't want to type their credit card and shipping info on tiny mobile keyboards. Why not do 1-Click checkout or Touch checkout while shopping on your favorite sites? Without having to download an app for every site you shop. It is doable today. Apple has the opportunity to make eCommerce sites as easy to checkout as Amazon's 1-Click, and more secure.

Perhaps "Fingerprint Payments" is the next killer app.