Of all the ISO standards I wish the US would adopt, ISO216 would be it for me, hands down. I recently needed to buy some A6 thermal paper, a size no one seems to offer anymore. And who cares! Why would they! I can just buy an A4 sheet and cut it in half twice, no fuss.
Same here. I wish I could just use A4 paper, but usually when I put something on paper it is to share with others, who will not have an easy way to store or process it. It has to be a widely mandated switch.
Like only allow A* paper for government forms or something that would force everyone to switch their paper handling infrastructure to A*.