Books have been written on this topic, and the controversy and squabbling about where the "hot" slots are placed in the casino are still on-going – more than sixty yrs after slot machine games were 1st placed in gambling houses.
The classic rule is that the superior slot games were installed just inside the entrance of the casino; so that individuals passing by would see actual jackpot winners and be captivated to come into the casino and play. Our deduction is that this is no longer true.
Just about all of the major casinos these days are grand complexes … it’s no longer possible to see inside from the sidewalk, so there is no longer a reason to position the ‘loose’ slots near any doors.
An additional classic rule is that loose slot games are placed on the major aisles in the casinos, again so that more potential players could see winning jackpots and be galvanized to play. Nonetheless, we find that this also is no longer a universal rule.
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 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 perspective about where to place the loose slot machines.