Retailer's will surely recognize that their value add is in the personal, friendly, and helpful atmosphere they can create with their staff. Square seems to have pretty much hit the nail on the head with 'Auto Tab' - eliminating the awkward, unglamorous part of the process (the obvious exchange of money) means that the coffee shop barista can instead focus on greeting the customer by name, offering the usual or taking a different order without reminding them of the money their spending or directly fiddling aroudn with cash or phones.

Sounds like a pretty ideal shopping experience to me. The only real benefit I see NFC having is that it can eliminate the wallet from my pocket.