Why should my tongue live on the roof of the mouth? What does the current literature say?

Across a variety of practices we are told to rest our tongue onto the roof on the roof mouth just behind our front teeth. It has been widely encouraged across Traditional Chinese Martial Arts, Dentistry, Orofacial Myology, Strength & Conditioning and in Ancient Yogic practices. When something has been repeated across a variety of disciplines across a long period of time there must be something to it.