The original argument essentially mirrored that of copyright (indeed, design patents were originally called design copyrights): To reserve ornamental designs to

The original argument essentially mirrored that of copyright (indeed, design patents were originally called design copyrights): To reserve ornamental designs to their creators, since nobody would spend time on such designs if they could be legally copied. Design patents came to exist with the advent of mass-produced goods which were both functional and ornamental. Copyright covered objects which one merely looked at (books, paintings, etc.) while design patents covered objects which were used for a purpose (flour mills, stoves, etc.); neither of these applied to a work of art engraved into the side of a cast-iron stove.