Today’s WoW (Whispers of Wisdom) got me researching polyphasic culture…and led me to this excellent perspective…and excellent answer to the question of…“why”. 
Here’s a teaser:
Perceptual diversity allows human beings to access knowledge through a variety of perceptual processes, rather than merely through everyday waking reality. Many of these perceptual processes are transrational altered states of consciousness (meditation, trance, dreams, imagination) and are not considered valid processes for accessing knowledge by science (which is based primarily upon quantification, reductionism, and the experimental method).
Transrational altered states of consciousness…I love that! Sounds like my college days in the early 70’s. 