As far as I know "luck" in the game on slots depends on their settings. At least in conventional casinos, this should be monitored by Supervisory services.
What exactly are "Supervisory services" doing? They make sure that the machine does not go crazy and does not start to give out Jackpot ??))
I think they make sure that the slot machine gives out a certain percentage on the winnings from the money of the game. This percentage should not be less than the established rules for gambling. This does not mean that in every game the slot should give out a win, but if you take a fairly large number of games