Books have been said on this topic, and the controversy and disagreement about where the "hot" slot machine games are installed in a casino are still on-going – over sixty years after slot games were first placed in casinos.
The classic rule is that the best slot machines were placed just inside the main foyer of the casino; so that casino fanatics going by would be able to see real jackpot winners and be stimulated to come inside … play. Our observation is that this is no longer the case.
Practically all of the mega casinos presently are behemothic complexes and now you can’t see inside from the sidewalk, so there is no longer a reason to situate the ‘loose’ slots near to any exits.
Yet another standard rule is that loose slot machines are positioned on the major aisles inside the casinos, again so that more potential gamblers could see winning jackpots and be energized to play. Importantly though, we find that this also isn’t a universal rule any more.
What casinos found over the years is that people walking down the busy aisles were frequently on the way to somewhere else. If they played slots at all, they would simply put in their loose change because they happened to be walking by. Win or lose, they would very often not stop to keep playing. And the very last thing a casino wants is for someone to win a jackpot by playing only a few coins and then not stay to put it all back in!
In recent times, casinos are constantly changing their perspective about where to place the loose slot machines.