One solid argument: xmpp failed as big tech (Google, Facebook) protocol and doesn't provide nothing radically better now: a ton of protocol extensions and incompatible clients.
Matrix on rise: got a business with EU governments, deliver new features (spaces), with voice channels probably will enter the real rival stage with Discord/Slack.
> xmpp failed as big tech (Google, Facebook) protocol
Did it? They embraced it, made external XMPP clients being able to interact with their own services, and then suddenly cut them off. For all we know, they are still using XMPP internally, they just don't federate anymore.
That sounds like a failure of XMPP. There is no reason for someone to need two message platforms other than userbases being split. If you actually wanted both for functionality purposes, it shows both of them are lacking.
It is a great pity that something that has created so much value for so many companies now somewhat languishes. A real shame. Not that xmpp isn't great, but it'd be so much better if the platforms that benefited from it had only contributed back more.
Like many extension-oriented protocols, XMPP works for internal use where the same organisation (or two closely cooperating organisations) control both ends, but doesn't work for communication between two loosely connected or unrelated parties.
Matrix on rise: got a business with EU governments, deliver new features (spaces), with voice channels probably will enter the real rival stage with Discord/Slack.