Are precious metals not physical wealth?

Anyway, Bitcoin is not inherently tied to any physical object either. People can trade Bitcoin for digital services if others are willing. It's just measured in relation to USD because USD is a very stable, globally-accepted form of currency that's easily transferable.

You could trade it for other physical wealth like gold, but you would have to have gold and transport it to someone, which is difficult and something no one wants to do, or pay for someone else to store it and transport the rights, which is also difficult and difficult to use directly anyway. Not to mention, gold is also a highly-volatile commodity. When the BTC/gold ratio drops, you don't know if Bitcoin is becoming less valuable or if gold is becoming more, because they both fluctuate so badly. With BTC/USD, you know it's Bitcoin that is moving.