Why Art?

“Measurement is always imperfect, and explanations are easy to invent”.   (Lehrer, Proust was a Neuroscientist,  p.3)

In  perusing a form to replicate our understanding of the world around us why do we chose the sciences over the arts?  Are they different?  Maybe we can measure emotions and are unable to explain a mathematical theorem.  I could not ask you what is Art, but I can ask you why.