I see it in the other way round, people who works in a casino exposed to lot of gambling actions means the outcomes too so they are probably aware of more people lose than winning that itself enough to make a conclusion unless they are not open enough to see the reality and see only they want to see.
It's just as another job, people got bills to pay so that runs on their mind than experiencing the fun but doing it once in a while isn't bad either like a waitress can go to a decent restaurant for dinner once in a while.
maybe the experience of seeing more gamblers who lose is also good for building the mindset of casino employees only to be slightly involved in gambling bets. but I have faith that they must also do gambling activities outside of their working hours.
casino employees may have their own way of relieving work pressure, such as going to parties that can be fun for them too, and can really get away from the gambling activities they usually do.