That's the main goal of casinos, to rekt the players as much as they can.
You said it right, this is a gambling business where the house needs to be profitable so they can operate the business continuously.
They even offer loans just for the player to go on. So if the player is not smart enough and just go with the flow, he will find himself in deep trouble even before he goes out of the casino. As a gambler, you should know your limits before you go inside. Don't be tempted with offers and other bonuses because that's their job, to keep the player as much as possible.
I've seen that most in movies but actually I have no idea what are the terms or anything related on why and how casino would offer a loan to its gambler.
There are loan sharks in a casino AFAIK, but are these people work with the casinos directly or they could be a separate entity? Either way, I don't think they would just easily lend a gambler without knowing the capacity to pay, so if a typical gambler plays in a casino, and lose and try to borrow, he can't expect to get approved.
As for me, I'm just lucky that I gamble at home most of the time, or... I think all the time.
I've heard before that there are loan sharks operating on casinos. Their target are those big time players who are losing. They let the player borrow huge amount of money in exchange of their cars, property's, etc. I've read that its a 2 percent per day interest in one of the casinos in my country, its really illegal and a problem for the authority. It will make the borrower really lose all his belongings if he will continue to lose.
I think, the casinos knew it, they are part of it, and they already knew who will be the person before they let them borrow a huge amount, they will be the one to offer so I guess they will get ID or just like what I've said before, any belongings the gambler can give for the borrowed money.