A while back, a friend of mine did "Warrior Dash." Basically, this is a medium-length marathon/ obstacle course, featuring mud. Lots and lots of mud. I guess the thought of running, sweating, and ending up coated in muck appeals to some people.
More recently, one of my tutors did a "Color Vibe" "fun run." This is a medium-length marathon, during which participants are pelted with paintballs.
In other words, at some point, someone, somewhere, went out for his morning workout and, while jogging along, gasping for breath, thought, "You know what would make this even better? Mud!" And then, when he told someone his idea, another person said, "Hey! Why stop there? Why not add assault and battery! With paint!" And then someone else said, "And you know what? I'll bet we could charge people to participate in this!"
And they did charge people. And people paid.
And people wonder why Americans are in debt.