So if you can't back a security with anything tangible then the true underlying value is 0. This means no one will buy it back if the currency falls to a value

So if you can't back a security with anything tangible then the true underlying value is 0. This means no one will buy it back if the currency falls to a value near 0. See the recent brouhaha about Titan (e.g.). Gold and silver at least have real use outside of "being pretty". That fixes the lowest possible value for gold to be above 0 somewhere. It does have some utile value, and that value is somewhere between 0 to infinity. The speculators are hoping for a "greater fool" who will buy their assets because you know, numbers go up. The criminals like it for the money laundering aspects. It's not a perfect money laundering tool, but it's certainly good enough for ransom ware (until recently when the US reclaimed some money from ransomware writers). There is some payment transfer capability, but here the utility comes at a price for some fee paid to transfer the money. The volatility keeps it from having very much utility as a store of value. Price was once over $60k but now dropped under $30k then back up to $34k. But volatility is not what you want as a store of value. You want stability and assets backed by something tangible. Largely it seems like the utility value is that "people think there's actual utility" when in fact, the utility is provided by speculators.