Biting is what remains when both arms are held and the head is not — in a grapple, on the ground, pinned under a shield. It reaches no distance whatever: the target must already be pressed against you, which is why it never appears in an opening exchange and often decides a closing one.
What it lacks in force it makes up in point. Teeth are piercing where a fist is blunt, so a bite that finds a throat, a wrist or a face does a kind of harm a punch cannot, and it carries the best Impact Tactical Advantage of any unarmed attack. It is also the most precise thing a person owns: a mouth goes exactly where the head turns, and its zone die is the tightest on the table.
Against armour it is close to useless, and it puts your face inside your opponent’s reach to deliver. Bite when you have nothing else, and bite something soft.