You visited the casino continuously, and you were one of the people that most money has gained thanks to the different games inside. Sigma, the manager, ended up having his eyes on you, because whether you want it or not, as much as you gained, you've lost too. That made Sigma have more incomes, and that benefits the casino completely. And the manager wanted to have a good relationship with the one that helped him raise the benefits of it, even if it was subconsciously.