What a flippant remark. Cash has been proven to be absolutely filthy and an effective vector for harmful pathogens, covered in bacteria and viruses, and also covered in traces of multiple illegal narcotics (one study showed that 79% of one-dollar bills contain traces of cocaine). And that’s not to mention ATMs - those things are gross.
I use public transport regularly, but I don’t go rubbing my hand over every single handle on the bus - for example. That’s the same principle as when you touch cash, since you’re coming into physical contact with surfaces that have been handled extensively by a large number of people and often exchanged for unsavoury things in unhygienic conditions.
Anyway, this discussion should probably be over on the Going cashless thread.