Comment by ralphm

Besides what MattJ100 wrote above, by itself this is also not true. You can tell Android to not optimize Conversations and allow it to run in the background. It will work just fine with a (usually idle) TCP connection. But for the typical user, having to instruct them to do this is cumbersome, and integrating with Firebase is easier. It does come with its own concerns w.r.t. privacy, both for the payload as well as metadata exchanged.