Appearance sells product.   

Initial contact with an item is usually visual. That first glance sets the tone for the balance of the introductory experience.  Appearance creates viewer expectations of something new and exciting, technologically advanced, or classically familiar.

Most important is projecting imagery that is appropriate for the intended market.  New electronic devices must look new, a sports car appear exciting and roadworthy, a computer mouse imply ergonomic comfort.   

Appearance should never hamper function.  Industrial Design merges image with product performance to result in a positive user experience.