Wearing a helmet should be a personal desicion for an adult.
I can see wearing one when eventing that makes sense, and in places without legal protection from lawsuits.
I have owned horses for over 46 years. I have broken both collar bones, fractured an arm, and dislocated my shoulder riding. A helmet would have given me no protection. I do not fear injury every time I ride my horses. That is my choice I alone will deal with the consequences. Shalom
db..I am sorry but that is just a silly statement. A helmet protects the head, not every bone in your body and no one here has ever stated that a helmet protects a rider from all injuries.
I also doubt anyone who rides fears injury each time they mounted or I doubt highly they would be riding for long. Wearing a hlemet is simply an easy step to take to add a little more precaution; it isn't fear regardless of how someone rides whether trail, western, eventing, dressage etc....
One fact remainsd however, how you conduct your riding at home or in an otherwise unregulated location is up to you. You choose not to wear a helmet, up to you. If, however, the rules of an association at a sanctioned/licensed event, which would require anyone mounted, regardless of age, to wear a helmet, you either grouse under your breath and comply or you don't ride and if you decide to try and make a statement and break those rules, you risk expulsion from the grounds and possibly higher sanctions from the related association.