This has always totally confused me. Why are they even called relays? They don't just relay. Some/most don't ever relay at all.

They are event stores (some of them are already quite large and have multiple years' worth of documents in them), and you can get information out of them with a request.

But they're decentralized (not fully distributed, but a hub-and-spoke network), so they're called "relays". Confusing, but trendy.