Stu Ungar
The basic basis for why Stu Ungar changed from gin to poker was that Stu was a bit too skilled at it. So good in fact, that no one was able stand up to him. Even the so-called experts who were supposed to be the best at gin rummy were crushed when they competed with Stu Ungar. One such gin rummy professionals was Harry Stein, called, "Yonkie". Harry suffered such a belittling defeat at the hands of stu that he apparently stopped competing in it as a pro and never showed up at a gin rummy tournament.
Certainly, with a notoriety like that it was not too long before people became shy of gambling against Stu Ungar. He could not find any matches and in his bleakness he began doing something no one had done prior. Stu issued starting handicaps to potential adversaries in the hope that they might just play against him if they thought they held an edge. He at will began from a bad position and one story has it that he even played with a constant bad egg. During the contest, he received a few words of wisdom that the absconder was at it one more time but stu assured that he was aware of the cheating and he would still come away with a win, which he did, of course.
The same trend followed Stu Ungar to sin city. He won so much that the poker rooms started asking him not to bet in their rooms anymore. The basis for it was that other casino visitors refused to be seated at the table if he were seated.
Stu Ungar is recalled more for his accomplishments in texas holdem poker but he himself always said that he was far better at gin rummy.
He beat Doyle Brunson in the WSOP in 1980 and became the youngest world champion. Due to his looks that made him appear far younger than he actually was, he was nicknamed, "The Kid".