it hurts less banging my head with a helmet on than off.
To me this is very simple, but some prefer something more complex before taking the easy decision of wearing one or not
I would have no problem with you telling people you think its worth wearing one because it hurts less if you bang your head. Its where you try to tell them it will save them from injury or death that I have an issue.
It happens so rarely that I'm happy to just put up with the ouch element and give my head a rub if I do bang it.