Why would you want to carry just one credit card when you can carry zero with Square (or Google Wallet)? If it is because of the "tradition problem", it's not

Why would you want to carry just one credit card when you can carry zero with Square (or Google Wallet)? If it is because of the "tradition problem", it's not much better than Square Wallet either: In more than one place I've been to the cashier was supposed to manually enter the last four digits of CC# manually for the transaction to get through. You'll have to carry a backup card with either Square or Coin. I like the vision of completely ditching the credit card far better, and the marginal compatibility benefit does not seem good enough for this to get anywhere in its current shape. Of course, things can change. (BTW, wasn't Google doing the same thing with a physical card for Google Wallet and ended up abandoning it?)