> I expect the majority machines that accept cash don't accept them,

Worse. What wound up happening was that the feds encouraged (probably grant funded, IDK) support for it and the only implementers were other governments and the easiest way to check the box was to make all your mass transit ticket machines and the like spit them out as change despite often times not supporting them as payment so a machine would eat your $20, give you a $2 ticket and spit out 18 items about as useful as Chuck E Cheese tokens.

This has mostly gone away as those machines have mostly switched over to cashless.