Down the road as mixed gas becomes even more common I wouldn't be suprised to see conventions change. Currently though there are still many shops who don't pump nitrox, they don't teach it and they don't have an analyzer. It wasn't long ago that you couldn't hardly get nitrox anywhere and in most place you still can't get anything with a high FO2 like a decompression gas. No doubt the safest is for everyone to analyze their own gas PERIOD. It's hard to go wrong that way.