Books have been stated on this subject, and the conflict and ruckus about where the "hot" slots are placed in the casino are still intense – over 60 years after slot machines were first placed in gambling houses.
The standard rule is that the very best slot machines were installed just inside the main door of the casino; so that potential players going by would see actual jackpot winners and be aroused to come unto the gaming floor … play. Our leaning is that this is no longer true.
Most of the mega casinos these days are immense complexes … it’s no longer possible to see inside from the sidewalk, so there is no longer a reason to situate the ‘loose’ slots close-by any exits.
An additional standard rule is that loose slot machines are placed on the major aisles inside the casinos, again so that more people could see winning jackpots and be galvanized to play. Importantly 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 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 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!
Today, casinos are constantly changing their philosophy about where to place the loose one armed bandits.