Easy explanation, they don't want the public to see the quality nor angles of coverage. This does not mean the cops/FBI did not see it or have it.
Oddly enough, when UFO sitings were becoming common in the 60's, the government encouraged the public to regard anyone who reported them as being crazy or perhaps delusional, which had the effect of making people afraid to speak about the topic unless it was to disparage anyone who believed in Martians. It's a wonderfully effective tool.
Because it's none of your business how covered the casinos are or aren't? Because it could show gaps that could allow thieves or copycats to exploit them? There are way more reasons to not make it public than there are to do so...
Much easier to bypass when you know the exact coverage areas. Same reason I won’t let people at work see our camera coverage. Why take your own knees out by showing your hand publicly? Damnit ... what the yuge one said, only slower.
Well, they don't have to show the coverage from every camera in the casino. I'm sure every square inch of the gambling areas are covered. Eh, I don't REALLY care that much. I don't go there...
Then maybe "they" shouldn't have had TV shows that covered the whole topic of Casino Security... There are Zero Gaps in good security... you see that when they show footage of robberies...of casinos... wait.. zero gap and robbery in the same sentence. NeverMind
So that no one can plan a robbery of the casino. If I can see camera angles I can defeat the security maybe. If I know resolution I can plan disguise level. I was in one in Colorado once with a camera around my neck (was taking pictures in the mountains prior) and security came to see me. They did not ask me to leave but did say no pictures, please.
Very few systems are perfect. While security through obscurity is not optimal it is a good thing to add upon the best effort you have.
I would bet that anyone who is going to plan to rob a casino will probably go have a look at security for themselves, not rely on the evening news for information.