Defense in depth means you don't reveal the content of messages if you don't have to do.

There's the issue of leaking IP addresses (even a VPN can often be traced to its owner).

There's plenty of people using their real (or at least easily traceable to real) identity already. Those people need to be able to have confidential conversations.

Even for nyms, pseudonymity offers totally insufficient privacy. We already know this from Bitcoin. But with text and image content there's vastly more clues for law enforcement, spooks and aspiring hostage takers to figure out who is behind a text.