Yet I'd wager most HN readers have a grand total of zero XMPP contacts. Myself included. Proving the GPs point.
XMPP is underrated. A lot of people are imagining Pidgen in 2011, but the protocol has been extended, the actively developed clients are good, and it avoids the heavier parts of Matrix (both client and server side.) I wouldn't be surprised if Slack's replacement when Salesforce inevitably fucks it up will be XMPP based rather than Matrix.
Even if Google Talk kept XMPP, they weren't going to save it, cause nobody used Google Talk. Facebook was by far the biggest XMPP-supported platform (though it wasn't federated), and they stopped probably cause they didn't see enough clients. Even Slack supported XMPP for a while, did you use that?