Have you ever worn a modern carbon fibre crash helmet ?
The motorbike lids I wore in the early 80's were very heavy and hateful fibreglass affairs.
A modern carbon fibre motorbike helmet is about four times the weight of a typical cycle helmet and costs several hundred pounds. Don't think there are many people going to be cycling in those when they become compulsory unless you can get your radical new unobtanium helmet to the market.