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.
With this, it comes to my mind if securities are also focused to scout the players especially those who are winning too much to somehow do an act to investigate if that player is doing something fishy why he wins. I just watched film like this and I wonder if the actual physical casino staff does check the player or observe someone that wins consecutively. Because believe me or not, it is also scary to win in a row even if your wins basically comes from luck.
Going back, Casinos in Vegas do really have big team of employees to ensure that they can provide the best service. That is why I think online gambling sites are the most efficient since their employees are limited to Cybersecurity experts, web dev, programmers and internal staff.
I am sure that the movies do not show even half of what the security services of the largest casinos currently have in order to identify cheaters. Technology is constantly evolving and I think that the security services are armed with the most modern computer systems.