You can trivially prove your gold ingot exists because you can just find it. It's also way harder to move your gold ingot out of your war-torn country, harder to transact with it, etc. The storage device does not hold the actual coins, just a private key that lets you update the public ledger that determines ownership (thinking the storage device holds the coins is a common misunderstanding).
I'm an open-minded skeptic, but there are real technology advantages to blockchain and cryptocurrency, there are a lot of scams too for sure - but that's not the interesting part. The HN median opinion on this is wrong as it often is (it was wrong about EVs and Tesla too).