I took a tumbling fall, rolled and cracked the back of my head on the pavement. When I saw the damage to the helmet I realised that without it I'd have been knocked out at least and possibly killed by the blow. So I always wear a helmet and so does my son.
My son, at 7, did a ramp jump on his new bike, just like Evel Kneivel he didn't stop and hurtled down a flight of concrete steps, teeth and blood everywhere, at nearly 13 he cycles everywhere, no helmet, still alive.