I just googled the return percentage of online casinos and saw different percentages that doesn't seem real. A slot machine can be written to pay out 98%, but its programmed to pay 90% and it's publicized that way to attract more people to play using that slot. Though one slot could be paying out that amount in the casino, yet my point is that no casino offers 100 percent payout that means if a slot pays out 94 percent for every 100 dollar bill spent on that machine the player losses 6$ to the casino.
That's pretty normal, why should a casino even pay our 100%? They can't afford it, or where else would they make a profit to run the casino. Casinos are private companies that need to make a profit to exist. Buying slot machines, renting a place, paying taxes and electricity all costs money. The online casino needs to run a website, have IT security and support staff and also pay taxes and electricity. We shouldn't feel bad about not getting back 100%, as this would also be no guarantee for us to get all our money back. There is still randomness involved and this will only make the jackpots a little bigger, but not change our chances of winning much.