The general approach seems to be "Head or brains are cheap, every body has one, but helmets are ( 1 expensive 2 hot 3 sweaty 4 dorky 5 etc). I have fallen on three occasions over
20yrs and had significant helmet damage on two of these. Concussions have cumulative cognitive defects. Minor short term memory malfunction so you don't remember new things as well, not good if you still face yrs of education or have a job with some intellect required. Personality changes, never for the better. 2-5% decrements in whatever IQ is. People may seem "OK" after head injury that is "minor" but subtle changes occur. This completely ignores major neurosurgical disasters, I am only talking about run of the mill head bounces with transient loss of consciousness, maybe scalp lac or abrasions. Minor aspects such as an ED visit for such will set you back the cost of a Trek 5700, plus a car to drive it around in if you are admitted to the hospital. Steve