Those folks up there at Visa sponsored the Olympics under the limitation that no other credit card could be used to purchase stuff in the Olympics, from a cup of coffee to an official hoodie. If you’ve never been to such an event it’s hard to imagine how huge the venues are, and once you entered a stadium in the morning, you’re not allowed to exit and return with your ticket. Which practically means that once you’re inside, you can either use Visa or cash, that’s it.