The operative word was "popular". The world uses Whatsapp and iMessages and not XMPP.
We're solving for the people who use WhatsApp and iMessage.
I wouldn't call XMPP "unpopular". But my real point ran a little deeper. That's the world we've consistently moved away from - interoperability seems to be treated as a bug, not a feature.
> (And no, this hasn't happened yet with XMPP. XMPP has, for a variety of reasons completely failed. We need to let it die and start from scratch with something actually designed with mobile devices in mind)