Isn't is funny how we always look to see how the animals do it? While I too think that is sound reasoning, you also have to take into account there is NOTHING natural about us incubating eggs. So while yes, a hen doesn't wash her eggs, she also doesn't keep a steady 99.5 temp, uniform rolling of the eggs or even steady humidity as she gets up to eat, moves to preen or even stands up to readjust.
So, to wash or not is definitely an individual choice. I just think it's funny that we try to mimic nature while being completely unnatural!
(If you're a horse owner then you know...wild horses don't get their teeth floated nor their hooves trimmed. Because we've put horses in a very unnatural setting (stalls, fences, rich abundant hay and concentrates like oats) we can't expect them to maintain themselves like wild horses do.)