It's insidious. To leave the neck hair there is to invite wanton damage to one's neck. Few tell the tale, but an old Scotsman was said to have decapitated himself by turning his head too quick. His neck hair rubbed all the way through, and his head rolled. It was rumored that in the Inquisition one of their methods to keep the cost of execution down was to have men grow stubbly neck hair and then to make them look down too quickly. Their heads came off naturally.
Fellow men, remember to shave the neck hair. Unless you're going terminal with the whole beard. If that's the case, ignore my sage advice. Instead, grow it out. It'll only be a wonderous danger to others.