The more I hear about the knife allegory the more I feel like we're all living in an episode of Seinfeld. My guess is, he probably didn't notice the dirty knife. Guys have awful peripheral vision. Or maybe it's unconsciously selective vision.

As for doing dishes, I'm self-consumed and epically lazy, so I probably wouldn't have thought to wash someone's dishes in the first place. Of course, the two bottles of wine I demand at dinner wouldn't boost those chances either.