Books have been written on this subject, and the disquiet and feuds about where the "hot" slot machine games are placed in the casino are still on-going – over 60 years after slot machines were first placed in the casinos.
The standard rule is that the best slots were put just inside the main entry of the casino; so that potential players going by would be able to see actual jackpot winners … be impressed enough to come unto the gambling floor and play. Our presumption is that this is not so anymore.
The majority of the major casinos today are jumbo complexes … you no longer can see inside from the sidewalk, so there’s no longer a reason to put the ‘loose’ slot machines in close proximity to any of the doors.
Another standard rule is that loose slot machines are located on the major aisles inside the casinos, again so that more folks could see winning jackpots and be encouraged 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!
Nowadays, casinos are constantly changing their philosophy about where to place the loose one armed bandits.