Earlier quoted context omitted.
I used to be an EMT. There was one week when I went to two different calls that illustrated this perfectly. Both riders middle aged, both at low speed. One wearing a helmet hit a pothole and had minor facial injuries despite going over the handlebars. The other no helmet and out of practice fell sideways and the first thing to hit the kerb was her head. She's permanently disabled and living in a care facility.
Anecdotal fear inducing internet story. Statistically 'in real life' extremely rare for this to happen.
Just like most forms of harm; most of the time that you take some form of insurance against a negative event, it's not necessarily because of the likelihood of that event, but the sheer totality of the harm that will occur if that extremely rare event comes to pass.