Books have been written on this matter, and the bickering and disharmony about where the "hot" slots are installed in the casino are still raging – sixty yrs after the slot machines were first installed in the casinos.
The quintessential rule is that the better slot machines were put just inside the main foyer of the casino; so that potential players passing by would be able to see jackpot winners and be tempted to come unto the gambling floor and play. Our theory is that this is not so anymore.
The great majority of the major casinos nowadays are massive complexes and now you can’t see inside from the sidewalk, so there is no longer a reason to place the ‘loose’ slot machine games in close proximity to any entrances or exits.
An additional classic rule is that loose slots are located on the major aisles in the casinos, again so that more folks could see winning jackpots and be energized to play. Importantly though, we find that this also is not 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 slot games 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 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 games.