Books have been written on this matter, and the controversy and disagreement about where the "hot" slots are installed in a casino are still raging – over sixty years after one armed bandits were 1st added to the gaming floor in gambling houses.
The standard rule is that the better slot machines were put just inside the main doorway of the casino; so that potential gamblers passing by would be able to see jackpot winners and be stimulated to come unto the gambling floor … play. Our inference is that this is not so anymore.
The great majority of the large casinos presently are behemothic complexes and it is not possible to see inside from the sidewalk, so there’s no longer a reason to situate the ‘loose’ slots near any doors.
Yet another traditional rule is that loose slot games are located on the major aisles in the casinos, again so that more potential gamblers could see winning jackpots and be influenced to play. Interestingly 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 the 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 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!
Nowadays, casinos are constantly changing their philosophy about where to place the loose slot games.