Volumes have been stated on this subject, and the controversy and discussion about where the "hot" one armed bandits are placed in a casino are still on-going – 60 yrs after one armed bandits were first placed in gambling dens.
The standard rule is that the most favorable slot machines were installed just inside the door of the casino; so that folks walking by would be able to see actual jackpot winners and be stirred to come into the casino and play. Our theory is that this is not so anymore.
Most of the large casinos presently are gigantic complexes and it’s no longer possible to see inside from the sidewalk, so there’s no longer a reason to place the ‘loose’ slots in close proximity to any doorways.
Another standard rule is that loose slot machines are installed on the major aisles inside the casinos, again so that more persons could see winning jackpots and be inspired to play. Notably 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 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!
Today, casinos are constantly changing their philosophy about where to place the loose slots.