Whether if the laws in your state require use of a helmet, you SHOULD wear one anyway!  Below are some common excuses and how to get around them:

EXCUSE:  It limits my peripheral vision

ANSWER:  You may have the wrong helmet for size and shape of YOUR head.  This may
                    require getting another helmet.
 

EXCUSE:  They're optional in my state.

ANSWER:  Whether if they're optional or not, you can still get a SEVERE head injury
                    without one!
 

EXCUSE:  It gets too hot wearing one; I sweat very easily!

ANSWER:  Solutions here include storing your helmet the basement or other cool location.
                    Another solution is to drive in the early morning, late evening, or at night.  Also
                    note that some helmets have optional vents, which may help a little, particularly
                    at higher speeds.
 

EXCUSE:  I only had one wreck with this helmet.  I'll just repaint the helmet to cover
                  up the scratches and save some money.

ANSWER:  A helmet is NOT near as "guaranteed" to save your head in another accident.
                    If you would have another accident, the helmet could just bust open like an
                    egg shell instead of protecting your head!  GET A NEW ONE!  The old one
                    should be thrown into the garbage.
 

Below is my original helmet that I wore when I had my accident on September 4, 2004.

Note the SEVERE scratches on the left side of this helmet.  Because I was wearing it, I mainly got scraped up pretty bad.  Without it, I could have been KILLED!!!  In the head region, only my face got bruised up and such.  This helmet was also equipped with an optional face shield, which was probably DESTROYED during the accident.  This face shield may have saved me from more serious harm to my face.

    Below is a photo of "mild" facial injuries.