Its only needed if $$ were withheld in box 12.
But, some states require that the two-letter state be entered in the first part of 13 (you know, NY, MA, IA...etc),..and then the Federally taxable amount of box 1 will end up in box 14
............but if box 12 is empty, and you live in a state without an income tax, then boxes 12, 13, 14 should be left entirely blank