Bitcoin BTC can be a currency only if its price is stable.
I agree, because until there is a stable price for cryptocurrency, it will not be used in the daily routine such as: shopping in the market, paying for utilities, etc.
Your thinking is too polarized. You are thinking all-or-nothing. There is no reason that Bitcoin can't be used as a currency while it is volatile. The reality is that it might be
less used when it is volatile, but that is not the same as
not used.