1. A lot more people are using Sign In With Ethereum than other kinds of signature-based auth to log into websites. The UX, while not perfect, is a lot more figured out.
2. SIWE lets the user share a cryptographically verified shared state of the user. For example, digital asset collections, reputation in a group etc.
Isn’t sign in with U2F exactly the same guarantees and issues? (Cryptographically proven pseudonymous identities, but no recourse if you lose your keys)
2. Once smart contract wallets properly gain adoption, you'll be able to do recovery (see: https://vitalik.ca/general/2021/01/11/recovery.html )
3. Lots of built-in anti-sybil techniques (eg. verifying that the address has nonzero balance is a pretty simple and effective one)