It's not a technical problem it's a value prop problem. Most users don't care about privacy.... Fundamentally there is more value for the network operator to g

It's not a technical problem it's a value prop problem. Most users don't care about privacy.... Fundamentally there is more value for the network operator to grow the network than for users to disclose their details. Email works perfectly fine without having to disclose your address book because no one owns the network and therefore do not care how many people are using email. Alternatively one could just allow users to choose whether to make their info public and then the client can just search a directory.