Can be many, if not greedy.. but can be broke all too ,but i never heard people earn money by just gambling.
But gambling gives them fun and excitement,that makes them gamble even they had no chance of winning.
I'm not sure that gamblers can get a very big advantage. For all people will surely use the greed in every victory he got or they will always be curious when they get their defeat. The key to not have a defeat in gambling is doing self control
Even with self control I have seen guys loosing a almost fixed amount of money.
In short, they get their salary change into btc a part of it and then gamble, if they win just in case they simply save and later loose it too.