My understanding of gold as a currency is that it naturally occurs with about the right frequency to be used as a money supply. It's rare enough you can't just make more but its plentiful enough to be in wide circulation.

Because it needs to have value everyone agrees on.

But we don't all agree on the price of bitcoin and I don't see why we would just because it's rare.

I don’t think it’s just the rarity. It’s also trustless, secure and easy to transfer. For ex, with gold, you’d have to carry blocks of it to move it around. And even then, you’d still don’t exactly trust it’s source 100% unlike bitcoin, where everything is in the ledger.

Pretty sure gold scales better than bitcoin as far as transactions over time.

you'd be hard-pressed to try and transport gold across borders in any significant amount.

The vast majority of people own derivatives, not physical gold.