Books have been stated on this topic, and the debates and interchanges about where the "hot" slot machine games are installed in a casino are still on-going – over sixty yrs after slot machine games were first placed in the casinos.
The standard rule is that the more favourable slot games were put just inside the main entrance of the casino; so that everyone passing by would see real jackpot winners and be aroused to come unto the gaming floor … play. Our attitude is that this is no longer the case.
Almost all of the big name casinos presently are mammoth complexes and it’s no longer possible to see inside from the sidewalk, so there’s no longer a reason to put the ‘loose’ slot machine games close-by any of the doors.
An additional traditional rule is that loose one armed bandits are located on the major aisles inside the casinos, again so that more potential gamblers could see winning jackpots and be roused to play. Importantly however, 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!
These days, casinos are constantly changing their perspective about where to place the loose slot machines.