Google Talk did have XMPP functionality, which allowed for SASL. [1] But of course, they killed this off because they wanted to dominate chat and messaging with their own proprietary protocol.

If they had not followed this strategy they would be killing in this market, even whilst supporting XMPP Federation. But they have chosen to release multiple proprietary products, so they aren't the lead in the market. Silly of them really, and it just shows you they aren't really the nimble company they once were.

1. https://developers.google.com/talk/open_communications

I doubt the decision to close up their protocols was taking lightly. You can bet that user lock-in is part of their current strategy.

Did any Google engineers ever reveal Google's true intentions for shutting down their XMPP offerings?

I'm still using XMPP to connect to GChat ... I use it every workday (via Pidgin).

Google stopped supporting XMPP in the sense that they stopped trying to change XMPP to fit their needs. They also started killing off support for arbitrary XMPP servers, e.g. you cannot run your own and expect it to work with Google Chat. (This was the most up to date link I could find.)[https://xmpp.org/2015/03/no-its-not-the-end-of-xmpp-for-goog...]

You can still somewhat use it, but it does not work well. Groupchats do not work at all anymore, and there is no message synchronization over it so any Hangouts client will populate messages an XMPP client never sees, and you cannot request chat history from the remote.

It is definitely not a high quality XMPP experience. If you want to use XMPP, you should probably be using duckduckgo's XMPP offering.

One day it will go away...

They killed it because Microsoft was leaching contact data from them without giving back.

https://news.ycombinator.com/item?id=11794776