Comment by giovannibajo1

Just like SIP, XMPP is one thing on paper (with all extensions) and a different thing in reality, where different clients communicate through different servers with different set of extensions.

What you can always do reliably is have a buddy list with status presence, and do 1-1 chats. In my company, with all Linux clients, we couldn't even manage to send files reliably across different clients.

What Google and Facebook need across a messaging service is much more:

* sending pictures, displayed inline * sending audio messages * making phone and video calls * sending money * being battery friendly through push notifications * having chat history reliably stored across devices * persistent group chats with advanced client-level tuning (eg: turn off notifications), again shared through multiple devices

Notice that most of these features require implementation and design on both the server and client level; not having control over client implementations means it might take many years to get a feature standardized and adopted by the majority of clients.

I think Google really tried to make XMPP go forward, but in the end it was slowly them down too much compared to competitors going full proprietary like Apple.