This was one of the few reasons why I opted for glass lens when I took on to do a quad protector headlight retro project on my 06.As for why it matters, I've seen the glass lights on a 1999 and 2000 model, and wow, even if the rest of the truck is in rough shape, the lights look brand new and gorgeous.
Mine came with polycarbonate, then retrofitted with xenon projectors, sold that set to a fellow mudder then did this. This also has PPF for added lens protection.