I see SIWE being pushed hard. It's like "hey Meta, you spent time trying to correlate all my identity to build an accurate profile? Let me make it easier for you by using the same identity on every app".
I think the point is that we can add privacy. This can include: * Providing an app-specific address for each app * ZK-proving any offchain credentials (eg. proof of personhood) that you want to prove about yourself