When is the last time you've ever seen any player at a casino ask the dealer to reconstruct the six or eight starting decks that are in a shoe? I've never seen that

You see the decks fanned out, each card visible, before they get shuffled and put in the shoe. It would require some sleight of hand from the dealer to cheat that way. If you're going to do that, it's much less risky to rig your slot machines or your craps dice or your Wheel of Fortune, where no one will ever notice any wrongdoing short of an audit by the gaming commission.