I've never seen it happen either - and I live in Poland, though I haven't seen it in my various visits to China, Germany and the UK either. Who actually does go into the restaurant bathroom specifically to wash their hands before the meal?
* wear a mask in crowded environments where showing my face doesn't buy me anything (I don't wear one at work, but do at the grocery store or airport)
* wash hands before eating (or at least use hand sanitizer)
* grip the exit handle of the bathroom with a paper towel and dispose of it on exit
Not exactly double blind demonstrated but low cost and this year has been much better than last (which may also be due to my immune system having caught back up, too, so YMMV)
I would say most people do wash their hands here, however I have seen everything. From people not washing them to people using the toilet, not washing them, and then sitting on the table for lunch.
My father would wash hands after petting a dog even, so I guess it's his germophobia that set the standard in my household.