For BTC, the real "uselessness" is the "decentralized network based on PoW mechanism"; for ETH, the real "uselessness" is the early decentralized network based on PoW mechanism, and the current decentralized network based on PoS mechanism.

BTC is not only "useless"; the usefulness of BTC lies in its valuable store of value and its utility for cross-border transfers, which is its usefulness.

Ethereum's "usefulness" is based on the applications built on it, providing settlement layer services for crypto finance and security for on-chain assets, which is its usefulness.

The so-called "uselessness gives rise to great usefulness" means that the "uselessness" of a non-reproducible decentralized network has given rise to the usefulness of BTC as a "global store of value" and the usefulness of Ethereum as a "global settlement layer". But there is one crucial question: if Ethereum truly provides global settlement layer services for on-chain assets, it also effectively possesses the function of "store of value". In other words, Bitcoin is not unique in this regard. Once its useful part is encroached upon, it will erode its long-term value; this is also why I say BTC needs its own ecosystem. Without an ecosystem, it will be confined to the narrative of "digital gold".