In fact, you can easily add a streaming server in the middle (and many-participant WebRTC servers do exactly this), it's just that you can't have it happen unintentionally.
[1] http://doc-kurento.readthedocs.io/en/stable/introducing_kure...
Or the more complex demo, for a video conference where all media is forwarded through the Janus server: https://janus.conf.meetecho.com/videoroomtest.html