Maybe because most of the world couldn't enter? Seriously Microsoft is an international company, don't see why they couldn't do an international competition. Especially when the contest page is in the "international language" English.
Loading User Information from Channel 9
Something went wrong getting user information from Channel 9
Loading User Information from MSDN
Something went wrong getting user information from MSDN
Loading Visual Studio Achievements
Something went wrong getting the Visual Studio Achievements