In the course of playing an RPG, there will come a time when the players will want to have their characters relax and have fun. And those characters deserve it. It is rough killing monsters, slaying evil princesses, rescuing fair dragons, and all that. To say nothing of trudging through foul and dank dungeons, dark and twisted forests, and the guts of your enemies. You would need a break too.
So upon their return to civilization, fun and frolic are called for. And as part of that fun and frolic the characters may want to gamble, and you should let them. Now you can.
Herein lie rules for quick and dirty gambling checks, several games, new feat and traits, and the Professional Gambler rogue archetype with new rogue talents. Who said fleecing a shill was difficult.