Agree there is a cost imposed.

nostr:npub1exv22uulqnmlluszc4yk92jhs2e5ajcs6mu3t00a6avzjcalj9csm7d828 doesn’t use phone numbers. SimpleX users can opt into a reusable address, which can be deleted without losing contacts.

I don’t see why Signal cannot investigate an identity approach that removes numbers, and improves privacy for a $6 million annual prize.