I think you're underestimating how entrenched the CC companies are in our society. I agree that they'll eventually be replaced, but I doubt it will be in the next year, let alone the next 5 years.
I think Coin is a nice intermediate step between 10 cards in your wallet, and no wallet at all. Intermediate steps are viable businesses. I think Square is an intermediate step, and they seem to be doing just fine. They're obviously going to be at the forefront of eliminating cards all together, but they knew that credit cards aren't going away anytime soon, and so they leveraged that to get their foot in the door with the merchants.
I think Coin is a nice intermediate step between 10 cards in your wallet, and no wallet at all. Intermediate steps are viable businesses. I think Square is an intermediate step, and they seem to be doing just fine. They're obviously going to be at the forefront of eliminating cards all together, but they knew that credit cards aren't going away anytime soon, and so they leveraged that to get their foot in the door with the merchants.