Thanks to organizations like riders4helmets.com more and more people are wearing helmets every time they ride. You only need to see a photo like this one once to understand how wearing a helmet can help save your life.
As the medical community learns more about the long term effects of concussion on the brain, there has been more focus creating better helmets.
One of the problems with the helmet industry (and we’re not just talking about equestrian helmets here) is that helmets work on a pass/fail system. They are certified or they’re not. There is no way to evaluate incremental improvements in safety, to point to one helmet and say it protects you better than another helmet. There was, briefly, a comparative report that was issued by an organization that evaluated helmet safety (it was in the UK) but helmet manufactures squelched it pretty quickly.
This is an interesting article about the current development of bicycle helmets. Definitely worth reading as it talks about how helmets are evolving for other sports that may help reduce concussions.