Yeah you are very correct it is not the winning that is making someone pursue or go after betting more when already or have already won huge amount of money it is the greediness, some set of people are just too greedy they want to make all the money in this life, I have a friend he won a very huge amount of money in sport betting because of greediness he wants to win bigger he used all the money he won to play 2 odd the bet cut, he became so frustrated and depressed and I told him to his face that his a very greediness person and if he continues like this he will continue to get into problem.
Winning is not what makes you become addicted to gambling it is greediness, my sister is a gambler when she wins money she does not bet or gamble for 1 to 2 weeks and that has been her principles for a very long time she's not greedy and that was why she was able to maintain it like that till date, just like you said Beparanf greediness is the main culprit that makes you pursue more to bet when you are already in profit.