It's not scam you just lose money and that's how gambling work. Don't gambling, it's very risky, when you win you will feel how easy to make money and that make it for some people became addicted to gamble.
You are right with it , that's how gambling works they are just going to let their players lose their money to them in able to feed their belly. That's the system of gambling works, at first you are just going to win for small amount in able to give you hope that you can win bigger amount. But in the end you are just going to lose, so before you are going to that scenario it is better to stop already.