That's...a pretty strong opinion.
Otherwise cash will still have it's issue during a blackout. For instance I'm not sure most shops would operate their POS during a blackout or without any connectivity, at least if there is any hope of resuming normal operations within days, it would screw the ledgers. ATMs of course are dead. Vending machines are also probably not ready for that (Japan has emergency ready ones, I can't imagine other countries doing that)
We're already in a world where cash is second class citizen, and it won't just get back to the "good old days" because of a temporary outage.
And it will also be a different story altogether if power/internet never comes back. Having cash stashed somewhere might not help you that much.