In all honesty though if you started using BTC as your main currency*, replacing your national currency, one day you'd have your money in BTC, the next day their value would be wiped out. We're not talking about a slow and steady decline, halving of the value in a decade. We're talking "no money to buy food for the next few months". Many people in countries with unstable currencies are particularly vulnerable to this kind of fluctuations because in general they have nothing to absorb the shock, no assets, no savings, etc. Unlike traders these people can't just wait for the rebound, by that time they're bankrupt.
BTC is useful for exactly the scenarios it's almost exclusively used in now: speculative transactions (buy low, sell high), or transactions for less than legal stuff and the overwhelming majority of proponents are in these 2 camps. There's a much smaller group of proponents made up of people who don't understand currencies in general (besides the basics, like spending them), or cryptocurrencies in particular.
I'm sure some form of electronic tender would fill this role you're describing but it's not BTC and probably none of the major cryptocurrencies on the market now.
* (putting aside the network capacity, number of transactions/sec, the cost of producing a BTC and of a transaction, etc. which make it completely unsuitable for the purpose of using the currency instead of just storing and trading it, which is probably the only significant purpose of BTC today)