Books have been set forth on this issue, and the controversy and face-offs about where the "hot" slot machines are placed in the casino are still taking place – over 60 yrs after the slots were 1st installed in gambling houses.
The classic rule is that the superior slot machines were put just inside the main doorway of the casino; so that people passing by would be able to see real jackpot winners and be impressed enough to come unto the gambling floor and play. Our view is that this is definitely no longer true.
Almost all of the major casinos nowadays are huge complexes … it is not possible to see inside from the sidewalk, so there is no longer a reason to place the ‘loose’ slot machines near any exits.
An additional classic rule is that loose slot games are put on the major aisles inside the casinos, again so that more people could see winning jackpots and be inspired to play. Notably however, 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 slot machines 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!
These days, casinos are constantly changing their philosophy about where to place the loose slot machines.