Books have been stated on this matter, and the controversy and arguments about where the "hot" slot games are placed in the casino are still rampant – sixty yrs after slots were first placed in casinos.
The standard rule is that the very best slot machines were positioned just inside the main entryway of the casino; so that everyone going by would see jackpot winners and be drawn to come inside and play. Our theory is that this is no longer true.
Practically all of the big name casinos presently are monstrous complexes and you can no longer see inside from the sidewalk, so there is no longer a reason to place the ‘loose’ slots close to any entrances.
An additional traditional rule is that loose slot machines are placed on the major aisles in the casinos, again so that more persons could see winning jackpots and be motivated to play. Interestingly 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 one armed bandits 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!
These days, casinos are constantly changing their philosophy about where to place the loose slot games.