Joshua on Nostr: I believe it is because most mobile wallets connect to someone else's public ...

I believe it is because most mobile wallets connect to someone else's public (centralized) node to broadcast transactions. That node can therefore see all your transactions.

It is not as useful if you run your own node and your mobile wallet connects back to it, but more useful as a default option for mobile wallets rather than connecting to a public node to broadcast.

It could probably also be used for projects like #meshtastic to broadcast transactions sent on the mesh to the Bitcoin network via any reachable mesh devices with an internet connection.