The bitcoin shouldn't be used as a a classic currency anyway, do you buy your bread or your coffee with gold?
Moreover that's true that the volatility of the cryptocurrency makes it actually unsuitable to be a real currency that your shops could accept.
In some country like japan, we can using bitcoin as payment in restaurant. But i prefer using fiat money for payment because its more practice and bitcoin is too valuable if we are using for payment
Crypto coins are very volatile which is not good to use for payment because it has potential to grow more and buy lot of things. Small earners might want to use fiat for payment because that can be use to invest for more possibilities though there are some stores that accepts crypto as payment and the government make it legal currency, everyone keeps it as their assets.