re: Poker & nuts hands grazy call
I think it has to do with the lower stakes and mistrust. I often see guys calling any bet post flop if they catch a piece of the flop - doesn't seem to matter how small a piece. They've seen enough crazy play in the past to never believe that a bettor has the obvious hand. On the the other hand, they're doing exactly what you want them to do - call with 2nd/3rd best despite the huge pot odds
against making the call. Unfortunately, the reality is that when they do that they're going to get lucky from time to time (approximately one in five times per your first example).