Most casino security guards used to carry guns. Nowadays, however, the only casinos where the guards remain armed are downtown, a few privately owned little joints, and a couple of hold-outs.
The main reason for the disarming of security is, as you might imagine, money -- money saved from having to shell out settlements for accidental shootings, money saved from the cost of the training required for each and every guard, and money saved from the high premiums charged by insurance companies to allow casino security to carry heat. We've heard of instances where security guards have misplaced their weapons, dropped them in the casino pool, pulled them in beefs with fellow officers, and discharged them negligently (one guard accidentally shot himself in the leg and another committed suicide with his weapon). So you can see why the insurance premiums are so high.
In addition, the guns are usually the property of the casino and/or they have to store the weapons on site (another insurance cost and an unsafe environment).
Another thing about the casino's money is the casino's money: It's insured. For max value. After insurance settlements, a casino never lost a dollar to a robbery.
Finally, the whole purpose of carrying a sidearm is negated when the security officers are told to never ever use or even present their weapon. Should they unholster a gun, they're completely on their own. For example, if an officer tries to help an elderly woman being attacked by using deadly force, he can be sued, and even prosecuted, as a private citizen.
All in all, any losses a casino sustains from a criminal action that an armed security guard might (or might not) be able to prevent are more than made up for by insurance covering the loss, in the savings from an unarmed staff, and in terms of the protection of casino patrons and the guards themselves.
