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?
I don't think altcoins are backed with something concrete physically, unlike real USD and other fiat currencies.
Although it is not backed by anything like precious metal, it has a high value because it is functioning like a normal currency, you can use it like money.