I can't understand why they ditched XMPP for corporative Google accounts. Our uni uses Google services but for their stupid chat I have to keep a Hangouts tab opened because most XMPP clients won't work with it.
Everybody I know moved on from XMPP years ago. Google and Facebook dropping their support was indeed big part of it. But all in all centralised protocols have proven to be easier, more stable and simply better. Want to roll out a new feature? No need to sit down with a committee for years or wait for all 3rd party clients to keep up: you just implement the feature yourself. Wait... what was the question?
Show me a centralised protocol that is better at interoperability between various services?