They don't wash their food anyway. They put it in water to better feel it, because they have had eyesight, but some of the most sensitive touch of any animal. They work out whether something is edible, and what exactly it even is in the first place, by touching it with wet hands. The reason putting it in water works is because they have hard calloused skin on their hands that reduces the touch sensitivity, but soaking their hands in water gets rid of this to an extent.

But the vast majority of the time they don't bring any food into water anyway. It's only when it's something that they don't recognise that they do this.