I think the 12v might be for the brake light/highbeam like what Ree mentioned, according to my shop manual, (Minarelli Electrical System)
" the primary ignition coil puts out 12v at approx. 20 watts to be used for accessories, such as a stop light circuit. The primary ignition coil supplies the power to drive the high tension coil as it's primary function."
I don't consider a brake light an accessory, definately a necessity, and a brighter 12v bulb makes sense. As for a 12v accessory, use it for a radar detector.:)