Minimising the chances of accident by riding well within my limits is exactly what I do when not wearing a helmet. Whereas you clearly choose to ride above your limits when wearing one.
It's definitely a choice but your definition of "sensible" seems rather flawed to me.
Exactly. By wearing a helmet I minimise the chances of injury whilst riding outside of my limits which is part of the fun in MTB-ing for me and perfectly sensible. If you like to ride within yours all but 6 times in 200.....good on you.