This is among the dumbest internet arguments ever.
G20/G21. The machines don’t care, my digital calipers, micrometers, rulers, and 3D CAD software don’t care which system is being used. So why should I have my undies in a bunch about which is better? I use the measurement system best suited for the task at hand - whether that’s metric, US customary, or light years.
As for not knowing how many inches are in a mile, that’s about the stupidest internet point ever. No one cares about that, well maybe some civil engineer might need to very rarely care in some unusual situation. The scale of measurement is wrong for inches. In fact, most people don’t care much about the actual distance away something is, they mostly care about how long does it take to get there. The odds are pretty good you have no idea how far it is from your front door to the grocery store in miles or kilometers. But you DO know how long it takes to get there. Whether by foot, bike, bus, or car.