I heard some higher officials including security people to mingle into gamblers like other gamblers to watch any kind of breach and then signal to control room if anything unusual happens. I have not seen any such people doing but I guess it could be another thing might be happening on physical casino just to ensure their environment go intact. From all these I just conclude running a physical casino is not a simple business rather than that, I may go simply owning an online casino.
I think that the presence of such employees depends on the size and profitability of the casino. The larger the casino, the more serious and professional its security service is. I think the biggest casinos in Las Vegas and that's where the best security services in the world are.
For me, as a player, the main thing is that I can enjoy the game and no one interfered with it.