I used to work for a company called Grips Systems that developed coinless gaming hardware, and helped install the systems at several casinos.
We developed the system with the casino operators and it was an amazing experience. Our first system would take the money from the card and in a split second credit the machine. The operators and players hated this because it became so impersonal, so we had to slow the process down and increment the credits on the machine one by one, and optionally play a sound for each credit.
The same had to happen in reverse, when a player cashed out we had to make a sound for each credit as it moved from the machine to the card. As techies we couldn’t really care for the psychology, but the operators even coined the term “warm fuzzy feeling” to describe the whole process.
Lastly, when a player hit a jackpot we theoretically could transfer the whole amount to the card, but the casinos wanted us to lock the machine up so that a manager could come and key the jackpot off and give the player a pat on the back.
So next time you play your machine think about the psychology that has gone into enhancing your gaming experience (as well as the countless hours of overtime i had to spend getting the damn stuff installed 
).