+1 on thinking “they are too chicken to tell mom they aren’t wearing a helmet”. If they’re actually trying to make a statement about somehow being cool, I think they’ve missed the mark.
Helmets mess up the do. All the cool kids know that.
(I’m not one of the cool kids though. I’ve noticed on recent rides that my hair sticks up through the ventilation cutouts. If I go for a run afterward, I have to make sure to pat down my hair. Otherwise, it looks like I’ve got some sort of punk hairdo going on.)