I don't know why you keep arguing this. You said that motorcycle helmets are "never" to be worn by bicyclists. I point out that there is not just one but -several- different companies cross-marketing DOT-approved motorcycle helmets for bicycle sports. Now you are talking about the "average" bike rider. I think you just have a narrow, inaccurate conception of the universe of all cycle sports and you've probably never been anywhere near a motorcycle. Look at these BMX kids, then look at the motocross kids.

https://crazybmxer.files.wordpress.com/2013/09/bmx-racing.jp... https://i1.wp.com/www.njmotocross.com/wp-content/uploads/201...