Amazon already does ship-to-store with its massive network of Amazon lockers in everything from Whole Foods to gas stations. It has a much more massive ship-to-store than any regular retailer because it’s not locked into a particular brand.
But Target and Walmart have a large amount of products in stock within an hour or so ready for pickup from small towns on up. That's not true for Amazon except in large cities. For most of the country, you still have to wait one or two days to pick it up if you order with Amazon.
I do wish Amazon would adopt ApplePay, too.