Use cases can be different. For manent you have one nostr identity and many devices. You automatically can sync notes and files between devices. Think about pasting a text to yourself from web WhatsApp and copying it from your mobile WhatsApp.
My use case is I have several chat bot instances in my local machine (could be a several different servers too). I have a personal assistant bot and create notes using the chat. Then I wanted to share those notes with another chat bot I have. It's not actually between different clients (I'm using same 0xchat client to talk with many nostr bot identities)
