I mean, basically any adventurous activity where you're moving [quickly] with equipment gives rise to use of helmets - kayaking, rock climbing, roller blading, skateboarding, skiing, skydiving, horse riding, ...
Can I ask, is it only safety equipment for cycling you're against?
It looks like you're trying to argue that people shouldn't wear helmets when cycling because people in cars; that have protection from a steel cage with crumple zones, and airbags, and seatbelts, and cushioned seats; don't wear helmets.
Like, sit in your car and get someone to launch a paving slab towards you; then sit on your push bike and do the same thing ... I'd do the first without a helmet, I definitely wouldn't do the second without a helmet (or at all). I can't see how you can find these situations comparable wrt indication of benefit from a protective helmet.