I'm going to disagree with this last point. On some ships, the casino is open to the atrium or to other parts of the ship. On the NCL Breakaway, we had a hard time dealing with cigarette smoke at the noodle restaurant next to the casino, and could even smell it on other decks, since the casino is open to the middle of the ship.
On other ships, the casino is smack-dab in the middle of the main deck. This is true on the Celebrity Summit, which I just sailed on. 90% of the public spaces are on Decks 4 and 5 and the casino is right in the middle of Deck 4. So you are probably going through the casino multiple times per day: from a lounge to dinner; from dinner to the evening show, etc.
I know that there are some ships where the casino is hidden on a lower deck, but I don't think that's the norm