Moving thread from IMHO to MPSIMS.
I did know one kid, incidentally, who got badly hurt because she wasn’t wearing a bike helmet. There was this big long beautiful forested rocky hill from the school down to the street that led to the subdivision where most of us lived. The path down was pretty steep, really too steep to ride your bike down, so those of us with bikes would walk them down – or better yet, straddle the bike while walking. Apparently this girl was straddling her bike and her foot slipped, so where she ordinarily would have just tripped she instead rode merrily down the rocky hill, flipped on the stairs at the bottom, and landed head-first on the street. She had stitches in her head for some time and was never the sweet girl she had once been.
The school had a very good solution for this, I think. They bribed us. Any kid who had a bicycle and walked it down that hill properly got a treat of some sort at the bottom from out of the principal’s trunk. EVERYONE took that route home before long. 
IIRC after that point we were also required to wear a helmet if we had a bike.