Casinos themselves kind of do this though, right? They give you a card with a balance to pay for games and load winnings, and sometimes they just add extra money to it if you've had a bad day to keep you playing. At least that's what I recall reading somewhere.
Comps are a thing for people gambling at a certain level (thousands of dollars). It’s less about keeping you gambling and more about keeping you gambling _there_.
They’re intended for people that gamble a lot - not so much if you lose, it’s more about the level of money your putting at risk over time. Long run, the casino will make money off you. They want you to stay at their property. It’s also a way to recoup losses if you’ve won a lot.
I had a good run on slots and craps once at the Venetian, and was invited to a slot tournament with a free dinner and 3 free nights stay. I then won the slot tournament. But my broader non-tournament play didn’t keep up with the level they were looking for (they wanted you to take the tournament money and spend it there) so the comps got fewer and weaker. They came back months later when I started playing and winning (show tickets, dinners, etc). A bit of play credit can happen but it’s usually not a lot unless you’re a high roller (tens to hundreds of thousands of dollars).
Before the casino cards it was the pit bosses that would keep an eye on you, so this predates surveillance technology, it’s old school.
