Price of gold also decreased in the history so nothing in this world a stable with prices so the difference between fiat currency and the cryptocurrency the fiat currency always losing the value but the cryptocurrency depends on the market condition so it is the real value of the cryptocurrency at the particular time it is not created or valued by anyone.
Everything that's subject to speculation is volatile (even fiat currencies), the only difference is the degree of volatility. Bitcoin happens to be an illiquid asset, but with more legacy players entering the volatility will decrease significantly.
If we look at gold's market, it is in the very top of the most liquid assets in the world, which directly explains why the price movements are peanuts compared to Bitcoin. Give Bitcoin a decade or two and it will be up there.
By the time Bitcoin is stable and very liquid, you can be sure that most of the upwards potential is gone just like gold. Gold won't miraculously double in value from here, people anticipate on single digit % movements and leverage them.