Because a robot can be powered down and require no resources for the flight there and back. They can also be stacked neatly into boxes. They also don't fight, or make little robots. They can stay at Mars forever, and no one will clamor to bring them back to Earth. And if your measurements are off and you kill one, you send another.
Which is really suboptimal, because it takes a lot less cost to manufacture humans.
A casino will notice you winning no matter how you do it. Since you are on private property, they can ask you to leave. If you don't leave, you are trespassing.
Actually, in Nevada it's a Felony. They don't ask you to leave, they ask you to leave in custody of the nice police officer.
The devil finds work for idle circuits to do.