Slot machines are reverse swear jars -- you put money into them and then curse -- and have the same effect on a functional mind: teaching you not to do that again. Homo sapiens is defined by being able to learn from experience and use tools. Slot players do the exact opposite.
The same emotions as a monkey with a stick, but the opposite contribution to progress.
Slot machines are the most existentially obvious scam: The fact that they're there proves that they make money for the casino by taking it away from everyone else. Anything the player says after that point isn't an argument, it's an error report from their brain. In fact, they shouldn't be called players, because that word implies skill. They're more involved in "playing" the casino septic system, where at least they affect when things come out the other end. And the fundamental laws of existence prove that they'll always push out less than they fed in. Slot machines have users in the same way drugs do, except even the gummiest crystal meth head isn't being conned into paying for his own body chemistry.