Yep. A lot of our ideas about the differences between clean and dirty are quite inaccurate. We carry our smartphone, we use it on the subway after touching doors, seats and ticket machines. Then we go home and wash our hands. And then we pick up our dirty smartphone with our clean hands again. And we do that for months without bothering to clean it. And then we get a call and press that thing to our faces. And most of us see no problem until it's pointed out.