There's been a few Bar Rescue shows in Vegas where they talk about setting the odds on bar video poker machines loose to attract customers. I've also seen machines set up for shills (bus entrance at Circus Circus) where they pay out often, but are played with the casino's money by people who appear to shut down like an animatronic mouse between busses.

He was probably cleaning dirty money by feeding it to the machines and getting a little less back all cleaned up and ready to pay taxes on.

Next time you're in a casino, pay attention to the machines that are visible to areas where lots of people aren't gambling. There's an Indian casino I spent a few days at that put all their loose machines right next to the food court.