They could, but it would be against the fundamental philosophy: > Relays don't talk to each other. Only the relays you are connected to will receive and store

They could, but it would be against the fundamental philosophy: > Relays don't talk to each other. Only the relays you are connected to will receive and store your events. This is an important aspect of Nostr. Relays don't communicate between them. For this reason, you should connect to as many relays as you want to send your data to.