Well, for me, I believe that casinos are not running on user's funds, except the un-serious casinoso out there, and those ones are likely to turn to scam sooner or later, casino is a very profitable business, there is no way a casino can be operating and depend entirely on user's funds, it means that casino is a time bomb waiting to explode, because the moment a gambler wins an amount of money that isn't available in their hands at that time, paying becomes a big problem, and that's how they will start having issues.
You can not start a casino with zero funds at hand, though it is possible to do, but it's not advisable if you ask me.
I am aware that when a casino starts with the funds of its users that is something very dangerous, in reality they are gambling everything there because they must have a large capital, because how can they do to hold the winnings of players with very large bets? as they can? a casino that did something like this here in the forum did not do very well, they started with a great campaign, and where many began to support the casino, but then everything was lost because the casino owner wanted to capitalize on the entry of players and thus to be able to take advantage of the system to quickly make good money and it was not like that, but they went bankrupt.