You've lost me, what's the connection between "people's ability to be publishers" and WebRTC messaging apps?

If you want to publish a WebRTC service, port forwarding will work fine and then you'll be bitten by the no servers restriction.

A messaging app doesn't have to require port forwarding, it can use a central server to broker the connection between endpoints. In that scenario, the "server" is on the internet, not the residential connection, but data comes from the endpoints.