Books have been written on this topic, and the bickering and feuds about where the "hot" slots are installed in the casino are still ongoing – more than sixty years after the slot machines were first placed in gambling houses.
The standard rule is that the most favorable slots were placed just inside the main doorway of the casino; so that potential players going by would be able to see real jackpot winners and be influenced to come unto the gaming floor and play. Our resolve is that this is no longer true.
The great majority of the mega casinos these days are herculean complexes and you no longer can see inside from the sidewalk, so there is no longer a reason to have the ‘loose’ slot machines near to any doorways.
An additional standard rule is that loose one armed bandits are positioned on the major aisles inside the casinos, again so that more people could see winning jackpots and be galvanized to play. Notably though, 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 the 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 perspective about where to place the loose slot games.