once cash is exchanged for metals, cash dies. But with cryptos, there is still some currency circulation. So now knowing this....
Metals can't act as money in the age of the computer networks, so that premise of yours is dead wrong, and so are the followup conclusions. Precious metals are a store of value. Cryptocurrency is the same + online money + a network protocol of almost infinite potential. Unless governments think they are smarter than the world's best cryptographers, this stuff isn't going to die. You don't un-invent something.
Interesting, what if cryptos where never invented? Then metals would have to act as money.
And technically, eagles are legal tender, people can use them as money, there just hasn't really been a reason to do that...yet.
Thanks for your comment!