Books have been stated on this matter, and the contention and feuds about where the "hot" slot machine games are positioned in a casino are still ongoing – 60 years after the slot machines were 1st placed in casinos.
The classic rule is that the most favorable slots were located just inside the main doorway of the casino; so that potential gamblers passing by would be able to see actual jackpot winners … be stirred to come unto the gambling floor and play. Our resolution is that this is not so anymore.
Almost all of the mega casinos presently are giant complexes … you no longer can see inside from the sidewalk, so there is no longer a reason to situate the ‘loose’ slot games in close proximity to any exits.
An additional classic rule is that loose slot machines are installed on the major aisles in the casinos, again so that more persons could see winning jackpots and be motivated to play. Notably however, 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 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 philosophy about where to place the loose slot machine games.