I do not think these people completely quit gambling. There are lots of professional poker player continues to gamble even after winning huge amount of money. And many lottery jackpot winners even engage more deeply in gambling after receiving their winning money.
It depends on the respective gambler how they take their gameplans like for some if they win big they will take a break to enjoy other activities from the amount,others cash out some and keep gambling while others who risks all of them to bet more and engage in high rolling bets so there are different types of players.We can say some quit,some take break while others keep gambling the usual way.