i'm singing in the rain...shower

you'll have to excuse me...i'm mildly sleep deprived. but thought i'd pose this question...what is it about the environment of the shower that inspires people to sing? and not your usual la la la, but uninhibited "no one's listening" (tho sometimes they are) singing? is it human nature to sing in the shower or is it learned? is it cultural? or do all people everywhere sing in the shower? And why do people sing in the shower? why not dance? is singing a response to cleanliness? does the act of showering release toxins or endorphins that cause a euphoria and inspiration to sing? people sing when they are glad - most do not break out in song when they are angry.

what is your take? and maybe next time you are belting out a tune in the shower, pause, and ponder why.