Why is the Tibetan robe designed like that, and what is the reason for that?

They live in the high terrain, cold climate, poor natural conditions on the roof of the world, which determines the Tibetan forefathers clothing basic features are thick insulation, wide and warm fat waist, long sleeves and long skirts. In the heat of the day or labor, according to the need to bare the right arm or both arms, will be tied to the sleeve at the waist, regulating body temperature, need to wear again, do not have to take off all wear; sleep at night, unbuckle the belt, take off the double sleeve, lay half cover half, into a warm sleeping bag, can be described as a multi-purpose.