Consider it people providing incentives for writing secure software. Perhaps the world would be a better place if everyone behaved honestly all the time, but t

Consider it people providing incentives for writing secure software. Perhaps the world would be a better place if everyone behaved honestly all the time, but that is an unstable state because it takes only a single person to deviate from the norms in such a world to exploit all the systems that weren't designed with bad actors in mind. The cashier situation is not comparable because it's not exploitable reliably. Unless you have an easily distracted cashier that can be cheated all the time. If that were the case I could see some less scrupulous people starting to do that.