>>95900366
imagine cutting a hole in your armor ruining its defenses entirely just for a hairdo that would constantly get shot off and shredded by AOE blasts going off and set on fire. And you'd need servants to waste their time trimming your hair so it doesnt get long and fall down into your shoulder joint mid-fight getting you distracted and slain
And hair doesnt naturally stick straight up so they have to lube it between every single action. Oh, and it entirely ruins the ability to stealthily hug a barricade and shoot over it without giving away your position. And enemy bolter and autocannon shots would constantly be hitting the stupid ceramite hair-cone knocking his head back throwing off his aim and distracting him mid-fight. And the biological hair and hole in the helmet makes it impossible for the space marine to have any meaningful NBC protection, so any nearby deathguard plagues and suddenly his hair melts away and the turbo-farts go down into his helmet and eliminate the skank of horus trooper.

And no it's not just an accessory on the helmet, the abadderps have it even with the helmet off.