As you've seen in some movies, casinos normally have coverage of everything -- sometimes by law. Lots of money flow in and out of casinos on a daily basis, so they need all sorts of cameras and sensors to make sure nothing is out of place when they start counting cash. You can ask me stuff about policies with card counting, player monitoring, camera installation, why I quit, etc.
Edit: Thanks for all the shown interest. I hope I've enlightened you all on the inner-workings of all those tiny little domes above you when you're doubling down.