I agree with you mate. Cryptocurrencies particularly bitcoin can be so useful at the moment but specifically for investment still. Volatility is the main hindrance why many of us still cannot adopt or considered cryptocurrency as our main currency. Development stage is on going though so hopefully in coming years it will become more stable to be use as mode of payments.
Volatility and adoption are the main factors for me why cryptocurrencies cannot be fully adopted yet as currency because there is no proper accounting of it. If I have a business then I wouldn't risk my profit by holding a cryptocurrency that may go down in value anytime unless the fiat value of it doesn't matter anymore if we would account all out sales and purchases in crypto in which case there is no need for conversion. If that time would come when it would be like this then mass adoption is here.