See also: training my dogs. It is even referred to by some as turning training "into a slot machine". At first one rewards the dog every time they do what was asked. Later, the rewards are only sporadically given (the slot machine). You do a thing,
maybe some coins or a piece of meat will come out. But the dog will continue to do what was asked even as the treats taper off. Eventually, out of habit and conditioning, the dog does what was asked without rewards being handed out. Also see also: the work of Pavlov.
The moral of the story is that if there were no profit motive on the part of the casinos, eventually gamblers could be conditioned to sit at a slot machine that has had the payout slot removed, thus explaining the woman playing "no payout" slots on her phone. I've often joked that my dogs must ask themselves sometimes, "he tells me to sit and my butt just hits the ground. Why? What's wrong with me?" One might get the same response from the woman were she able to give you an honest answer. Like my dogs, she has probably long since forgotten why she even plays slots on her phone.