I think the argument for failure is because barely anyone is using it directly with an XMPP client. But as a back end layer for other platforms, it's a smashing success.
According to the XMPP offical website to add some numbers to what you mentioned:
~800 million WhatsApp
~200 million Zoom
~4 million Grindr
Matrix is also (one of) the more popular decentralized chat platform, which is built on XMPP.
I wouldn't at all be surprised if there's chat services that have you connect your local app with XMPP to, and get a simple UI layer that only connects to specific servers and other provides other config settings.
I've also heard of other uses besides chat, like for server management or video game multiplayer games for example. It's a great protocol that's provides delivery logic, accounts, etc. but keeps the actual messages simple and flexible for whatever you want to do.
I think SMTP "won" from being focused on email management instead of a more general protocol for multiple uses. (not that you can't do wacky things with SMTP, of course)
XMPP is in actually in Cisco VOIP too, and that Cisco VOIP Unified Communications [1] stuff is incredibly popular.
The client side Cisco Jabber app is Cisco's version of it that works with their VOIP.
Believe it is both Client & Server, and that is an interoperable implementation that looks like a reskinned pidgin somewhat in older versions, but has a great deal more functionality now, and looks capable of doing VTC and other things [2]
Considering how popular Cisco VOIP is, I think lots more people have XMPP functionality than they realize
His other example, Snikket, is self hostable and interoperable with the wider xmpp world. The pattern is largely related to companies wanting to build walled gardens. On that basis, most open source tech has "failed" in the sense of having created greater value in VC backed companies with marketing departments than in communities without them. It isn't really surprising that it works that way, and IMHO it isn't failure.
That's really the key and the end of it - SMTP was big enough that all the companies had to work with it, even the ones that originally wanted to walled garden (Lotus Notes and Microsoft Exchange are two big names, even now Exchange still has X500 stuff in there).
The closest thing to that which chat has is text messaging, and I'm honestly surprised that MORE platforms don't have a text messaging "bridge" of sorts.
Only for two-way chat, plus the default is still not encrypted (using Signal protocol) for WhatsApp.
In short, data-at-rest still can remains unencrypted for majority of the messagings on the WhatsApp’s server for all those who may be interested in them … UNLESS you enabled Signal/Encrypted option for two-way.
Group chat for WhatsApp?, it’s still the proverbial pants’ down.
According to the XMPP offical website to add some numbers to what you mentioned:
Matrix is also (one of) the more popular decentralized chat platform, which is built on XMPP.I wouldn't at all be surprised if there's chat services that have you connect your local app with XMPP to, and get a simple UI layer that only connects to specific servers and other provides other config settings.
I've also heard of other uses besides chat, like for server management or video game multiplayer games for example. It's a great protocol that's provides delivery logic, accounts, etc. but keeps the actual messages simple and flexible for whatever you want to do.
I think SMTP "won" from being focused on email management instead of a more general protocol for multiple uses. (not that you can't do wacky things with SMTP, of course)