Just remember that our current "big" relays are incredibly small if nostr succeeds. Relay hints being signed also help heal the network. Even if everyone uses the hubs, outliers can still force hubs to route to them, if hubs want any content with inbox-model-generated hints.
Discussion
do any gossip implementations post replies to the relay hint from the note it's replying to?
Coracle doesn't, but I do publish replies to the user's NIP 65 inbox relays. The reason being there's not really a mechanism to self-hint that I'm aware of. I suppose `r` tags could be used, but those are frequently used for other things.
there really needs to be a DHT keeping track of notes by content hash, then choosing relays would be irrelevant, and getting traffic would happen by aggressively caching and advertising the cache content hashes and updates.
it will be interesting to watch how the self-healing p2p stuff will develop. there's a big puzzle in the matter of spam resistant indexing.
DHTs do not scale well with small pieces of content. The hash map ends up occupying almost as much space as the content itself.