But the USD was backed by Gold until Nixon finally closed the window in 1971. The Saudis helped him do it, which is why they looked the other way when the Saudis financed 9/11. Legal tender laws can't force another country to accept USD either, thanks again Saudi Arabia. The vast majority of Americans still don't realize that. They also think that their bank has a vault where they keep everyone's money.
As far as crypto goes, until you see prices quoted in crytpo, it's still a speculative purchase. There's nothing wrong with that, the danger is when people think crypto is equivalent to a physical asset, like gold. A paper wallet or a Trezor in your safe is not the same thing as a gold (or even a silver) coin. You might just as well be buying paper gold, i.e. if you can't hold it in your hand, you don't own it.