Also, you force people to take a break. It's pretty common in finance to require a 2 week consecutive holiday every so often: one justification being that if someone was cooking the books, the person taking over their role would probably stumble across it.
Or for the Sarbanes Oxley rules. We often run into headaches at my office because our second check signer is a general manager based in Canada 75% of the time which ends up holding up any checks over $1k.
The complete lack of internal audits was something that struck me about this story. Million dollar game pieces constantly disappearing, and no one in the company was in a position to notice anything was wrong.
They didn't disappear, it appeared that he'd put them on the packages as expected and then people won the prizes as expected.
They were not security pros. Everything was left to trusted people. They didnt have people witness the opening of envelopes and installation of game pieces. So nobody saw that he was stealing. Today we know better.