I want to ask why there are sleeves in Tibetan dance, or the origin of sleeves in Tibetan dance!

That's not a water jacket. One sleeve of their clothing is because of national habits, and the other sleeve is because of national aesthetics. It's like cheongsam has been worn on your wrist since ancient times. Put it down to warm your hands when it's cold. It's just that they will be thrown away during dancing or sacrificial dancing, and will be interpreted by dancing and developed into such a sleeve, which makes you look like a water sleeve. In fact, both traditional Chinese opera and classical dance are called sleeves.