There are three main reasons why curling membership is swelling around the globe: fitness, strategy and fun. From a fitness standpoint, some curlers walk 2 1/2 miles per game on top of receiving a tremendous upper body workout (see sweeping below).
From an intellectual standpoint, the sport is unparalleled. There is no game where strategy is more important. Like a game of chess, each shot is chosen cognizant of shots to be made a half-hour or hour into the future.
It is a sport that finely balances the social and the competitive instincts of the athletes like no other. You shake hands with your opponents before every game, spend two hours clashing with them and then buy them a beer afterwards. This is what the world is discovering.