one thing that surprised me to learn about casinos: it's absolutely fine to let people win back 99% of their money on average, because if that is indeed the average across all customers, that still leaves the casino with 1% on average. games can be chosen or designed so the odds are always *slightly* in favour of the casino over time, even with the occasional customer winning a big jackpot. if you were setting up a new casino with no prior experience, you'd need to tweak the games a bit to get the balance right, depending on the behaviour patterns of your clientele, but that's just a matter fine tuning and monitoring the accounting sheets for feedback to make sure you're at a sufficient profit margin.
Discussion
RNGs are alot more complex now, the more digital it goes the more random all the machines become aka the more losers. Thats why gamblers like to hit the new machines fast for the first few jackpots the algo spits out but as the algo becomes more complex and more machines are more complex you have less winners. Well i wont say less winner but less likely hood of consistency spread across all machines as a whole.