Although cash still reigns supreme in the vast majority of countries, it may be sidelined sooner rather than later. If cash were to disappear, trust in the currency, a key public good, would be dependent on the creditworthiness of private entities.
With bitcoin and other crypto assets we have seen large and unpredictable price swings and outright cyber heists that may expose people to the risk of losing their savings; this demands that central banks take these risks seriously.