It'd have a similar role as gold. In cases state failure, you absolutely do have people trying to buy groceries with gold coins. But it's inconvenient, and people tend to run out of gold coins. So the incentives - when times are good - run toward normal credit systems like Visa & Mastercard, and hard currencies gain adoption only when times are bad.
Similarly, we've had folks transacting personally with Bitcoin in Venezuela and Zimbabwe. It tends to work out fairly well for them - at least their money holds value. But transaction costs in Bitcoin during the 2017 bubble were about $20/transaction, which makes it a pretty high-friction experience for groceries. There's a lot of market pressure to create other solutions (Lightning Network? Stellar? Local fintech companies?) for payments when Bitcoin costs $20 for everything.
Similarly, we've had folks transacting personally with Bitcoin in Venezuela and Zimbabwe. It tends to work out fairly well for them - at least their money holds value. But transaction costs in Bitcoin during the 2017 bubble were about $20/transaction, which makes it a pretty high-friction experience for groceries. There's a lot of market pressure to create other solutions (Lightning Network? Stellar? Local fintech companies?) for payments when Bitcoin costs $20 for everything.