They didn't explain why players roll around on the ground and shriek in pain when someone lightly brushes up against them. From what I can tell that's integral to the sport of soccer.
But if you know the answer, why do you ask for an explanation? Memory loss?
Exclusive “secret” film of the Italian team preparing for the World Cup ;):
http://www.youtube.com/watch?v=QRO626ImQek&feature=related