Any technology that is pro-society should never be over-centralised (e.g. control over citizen freedoms to use that technology).

Physical cash is material technically government-controlled and -produced, but people can freely trade it with great independence.

I don't think we'll have a big problem here. People's drive to freely trade critical resources between each other is so strong that they'll create their own currencies if they need to - which is exactly what the burgeoning ecosystem of cryptocurrencies already is.