I think the thing that surprises me even more is that they don't realise that cards which are quite openly stacked A-B-C-D-A-B-C-D etc will, when dealt into four hands, produce all the As, all the Bs, etc.
I don't doubt that it might fool some people, but there's little chance that anyone with an analytic mind (layman or not) would be fooled by it at all. It would only take them a moment of thought before it became obvious. Ditto for the idea that cutting mixes the cards. I've seen smart laymen spectators figure out much more subtle puzzle tricks than that.
For that kind of spectator it's necessary to obscure the state of affairs so that they think the cards were mixed (either by false shuffling or time misdirection or whatever). At that point the final cut just becomes the icing on the cake in their mind, not the action which mixes the cards.