I don't quite live in a socialist political environment, yet, so I have no fears about our states mandating such things anytime soon. This is a common sense issue. High visibility clothing is much more conspicuous than the generic variety, whether you are riding on the roads or frolicking through green pastures. My own eyes have proven this to me beyond any reasonable doubt. It's worn by police and other civil safety workers, construction and dock workers, certain military personnel, aviation workers, etc. That also speaks volumes. It draws the eye to its wearer, not necessarily convincing the brains of the skeptical of the obvious potential benefit(s), but, really, who cares about that? It costs no more than conventional gear, so what's the BFD?
Since I believe that it makes one more visible and I know that being more visible to others while riding a motorcycle is a good and smart thing, safety-wise, this is an open and shut case as far as I'm concerned.