One successful dive can win you the game in soccer. If eating shit the right way in mountain biking or in skiing could win you the competition you can bet your ass people would do it. Yes it conjures a bad image but it wins games. Also, professional soccer players are some of the most fit athletes in the world, certainly more so than mountain bikers. Mountain bikers have balls of steel though - no doubt about it.
Besides, the video is a horrible comparison. You're comparing people in one sport who are purposefully diving to people in another sport who are eating shit. Obviously the latter is going to look more extreme. Especially when the latter sport is considered to be an extreme sport, while the former is a competitive sport.
That's like comparing Nascar crashes to people getting injured in baseball. You crash in Nascar - you die, you eat shit in baseball - you walk away with a pulled hamstring.
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