[MarkMc]

Why hasn't some cryptocurrency replaced the bolívar as the unit of currency for most private transactions in Venezuela?

Given the Venezuelan government's poor economic management and tight restrictions on foreign exchange transactions, if cryptocurrency was going to overthrow fiat currency anywhere it should be in Venezuela.

[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).