[azernik]

I think you are aiming at this result, but to spell it out:

Because most cryptocurrencies are not suitable for use as a currency. They are not stable units of account, are not as easy to exchange on an everyday in-person basis as cash, and are only a stable store of value by comparison to complete disasters like the bolívar. There are attempts (e.g. https://basis.io/ or https://tether.to/) to make a crypto-currency that fills this niche, but they have flaws (Basis isn't deployed yet, and Tether is a bit scary - it's backed by a single company that theoretically owns one dollar for every Tether coin issued).