The idea that helmets provide a 'catch-all' protection for their wearers & believers is little more than an article of faith among honest scientists, and there are many reasons to believe that the methods of Class 1 evidence would be insufficient to prove it.
Yet we are forced by law to wilfully purchase & wear an unnecessary oil-based product:
$ All in the name of faith
$ All in a bid to protect us
...quick little caveat though - if you're a paying passenger in a bicycle taxi none of the above applies - according to government rationale, your $$$s will protect you - clearly??