As Goatboy elegantly pointed out, there are far more people that participate in "bodybuilding" than any other physical activity/sport. The fact that its pinnacle, the Mr O is now in a plight of implosion goes to show how much of a train wreck pro bb is.
In comparison to any football sport, it would be as if 2 people attended the Superbowl/World Cup final despite playing as an amateur.