To explain more, for e.g., we hear that the USD was backed by the convertibility of this currency to precious metals until 1971. Now, what are altcoins backed by such as Ethereum or Litecoin? Are mathematical calculations performed by ASIC miners any useful in the real world?
What USD backed up is backed up by what? This will eventually run out of place. What is valuable is valuable because we give it value. Cryptocurrency is one of them, and they are backed up with nothing like the others (except some stablecoins). The only difference among USD and BTC is that USD is belong to state, but BTC is the public money.