[thehappypm]

Gold is not a used directly as a currency anymore, in part for the reason that it's hard to control the value of an asset. It turns out that having some control over a currency's inflation/deflation is very powerful and good for economies to function.

[rawtxapp]

Fiat currencies fluctuate too, even a big pair like USD/EUR has a high of ~0.9 and low of ~0.8 this year and if we are talking about smaller currencies like say the Turkish Lira, you're looking at much larger changes.

Gold isn't used directly because it's not convenient, are you gonna transport a heavy metal that you can't divide into small portions to pay for stuff? No! Lightning network wallets makes even tiny payments of couple satoshis very easy/instant/almost free.