You see the problem is...
.... that all the evidence is that many health workers forget to wash their hands when they should. Not a new problem, but something that has been harming patients for 50 plus years. (Difficult to take it further back because of course cross infection wasn't so widely understood.)
Ironically, many years ago, I crushed some of my fingers when I was playing a very minor role in a hand washing research project. No connection between the two, just a coincidence. The nurse who dressed the wounds didn't wash her hands or use aseptic technique. She got very cross when I commented on this.
The point is, this isn't just washing your hands before dinner, or after you've had a crap, it is washing after every physical contact with every patient, over again, all day long. And people don't do it.