Your "facts" are not borne out by reality. Nations have mandated helmet use and seen zero increase in safety and in fact drivers on average drive 3 inches closer to bike riders when they are wearing a helmet making them less safe. Helmets cause their own problems for riders outside of their infectiveness as well. Not everything is as black and white as it seems. Many choose not to wear a helmet for very good and valid reasons.

To the point, as it relates to boxing a helmet wont help anything but perception as the meager cushioning does precious little if anything to slow the skull/brains rapid acceleration/deceleration during/after a punch.