Protect not punish

One of the concepts that new (or young) players have is that the laws of chess are as much about protecting them as it is about punishing their opponents. During a school coaching session yesterday there was a player who wanted to change their move on the grounds that their initial move was 'bad'. When I pointed out that they had taken their hand off the piece and that meant the move stood, they argued that it was a silly rule. My counter argument was that if she was allowed to ignore the rules, so was her opponent, and that her opponent could now checkmate her by simply playing two moves in a row. I'm not sure how convincing that argument was, as she then simply resigned and started a new game.
The concept of rules being a protection applies in other ways. One of the most common causes of disputes is 'touch move' where one player claims their opponent touches a piece, and the other denies it. In the absence of witnesses the normal practice is to accept the denial, unless the player concerned has 'form' in this area.  While some may argue that this is unfair to disbelieve a players claim, it does protect players from false or mistaken claims made by an opponent.
Of course this did not help in one case I read about recently. During an international junior event a player moved while the opponent was away from the board. Then before the opponent returned, they played a move for the opponent (with a rook), but returned the piece to the start square. When the opponent returned and played a different move, they claimed the opponent had touched the rook and had to move that instead, which lost in all cases. Normally this would be rejected by the arbiter, but as the games were being played on DGT boards, the 'fact' that the rook had been moved was registered, and the claim was upheld!