Do you think client server architecture won't be able to utilize nostr for identity?

I've been thinking about this, and I feel like we have Client Relay architecture (most nostr apps), but there could also be Client Server Relay apps.

If I just want to make an app and host it on a server, but not deal with identity management myself, I could have you sign a nostr event with some challenge and then use a session cookie like a normal client server flow.

I just see it as another way to prove your identity to a server to access authenticated information. I don't think client relay flows will replace every usecase for an app.