The basic reason for why Stu Ungar changed from gin rummy to poker was that Stu was a little too good at it. So skilled in fact, that no player was able stand up to him. Even the apparently champions who were supposed to be the best at gin were defeated when they faced Mr. Ungar. One such gin professionals was Harry Stein, called, "Yonkie". Mr. Stein suffered such a crushing blow at the hands of Stu Ungar that he evidently stopped playing it as a pro and never showed up at a gin rummy tournament.
Certainly, with a honor like that it was not long before everyone became weary of competing against mr. ungar. He couldn’t find any matches and in his bleakness he started doing something no one had performed before. He issued beginning handicaps to potential adversaries in the hope that they might just play with him if they thought they held an edge. He deliberately started from a bad arrangement and one account has it that he even competed with a constant absconder. Amid the match, he get a few words of wisdom that the bad egg was at it once more but stu guaranteed that he knew of the dishonestly and he would still win, which of course, he did.
The same problem followed Stu Ungar to sin city. He won so much that the poker rooms started asking him not to compete in their respective premises anymore. The reason was that other casino customers would not be seated at the poker table if he were playing.
Stu Ungar is recollected better for his accomplishments in texas holdem poker but he himself always insisted that he was considerably more accomplished at gin rummy.
He beat Doyle Brunson in the WSOP in 1980 to become the youngest world champion. Due to his looks that made him seem far younger than he really was, he got the nickname, "The Kid".