These shenanigans before displaying the final result can have quite a lot of psychologic effects.

Back when I started programming, I did simulate a jackpot machine in software (no money involved). The final probabilities were fair, but I added a twist while rolling the images: before stopping, the probability of having 2 or 3 of the same image was quite significant... My younger brother was instantly hooked to it. The trick made him overestimate the probability of having 3 images the same, as he was seeing this pattern quite often just before stopping. This made me realize of fucked-up casino can be, while still abiding by the rules