It's very complicated to verify the purity and dimensions of said metals. Back to the Lydian Empire, the coin minters were using some of the ideas of Pythagoras to mess with the diameter and weight. Imagine how much you can tamper with those today. For everyday transactions, în case of power or internet outages, people would rather turn to barter locally. Then again, I imagine priorities would be very different that day. Plus, just the top 10% would transact in sats in meaningful volumes anyway.