I think the problem to solve is that you can’t do it for free. Currently you get charged fees for every transfer, something that doesn’t happen with cash.

Plus this is a single standard. If I go to pick up a trademr purchase I’m unlikely to be able to pay with Venmo, because there are a dozen other options and no one has heard of any. With a government backed option, people can start advertising that they accept it, and vendors/banks know where to focus their efforts.