I once ejected myself from my bike at a good rate of knots and entered a car via the rear window using my face to break the glass [please don't ask how this happened, I am sure dr_pink will happily give full details if you were to ask nicely, she even took photos, macabre if you ask me]. My head went through the glass just under the top edge of the metal frame. If I had been wearing a helmet there is little doubt it would have caught this top edge and abruptly stopped the forward motion of my head which then would have been whipped backwards.
This is by way of countering the ad nauseam stories of damaged helmets so therefore it saved my life.
If the pros stopped wearing helmets, sales would collapse. So I don't look like a pro, why would I pretend to be one?