Wal-Mart in my area accepts "Wal-Mart Pay" through their mobile app, but when you use it... you don't get a physical receipt. The problem is... a lot of the time, they ask for receipts as your leaving the store. And I don't like the idea of handing over my phone for 2/3 minutes as someone hunts down something on my receipt.
Not only that... but would you really trust Wal-Mart's Servers with your Credit Card information? I agree with everyone else, Apple Pay or Samsung Pay is far superior and more secure. CurrentC and Retailer's App Suck.