This statement is inarguably true. Of course, as the price of what you purchase changes, its value also changes. Same thing is trye even with physical commodities. They may also lose or gain value. But this doesn't mean that you cannot use crypto as money or as a mode of payment just because it is volatile. Even fiat is volatile. You buy dollars, per se, then you'll trade it with euro when the price suddenly dumps. Does this mean you cannot use the dollars that you bought to purchase goods? Of course not! The issue here lies on the volatility rate and movement, how high and low its volatility is and how fast does it change within a specified time.