It's used by a lot of the big commercial platforms because it's well understood and has libraries for every system and language ever invented just about. Eg. Zoom and Jitsi both use XMPP (Zoom for Chat, Jitsi for chat and signaling), WhatsApp used to just have their entire backend be an off the shelf XMPP server, Cisco Jabber which is still popular in "enterprise" uses it, etc.
And for other individuals just wanting to talk with their parents it's just a chat app, they don't care if it's XMPP or not, Conversations is just really nice to use.
With privacy minded folks and people who think we should just agree on using the IETF internet standard for instant messaging instead of 5 different proprietary messaging apps and 3 apps based on experimental "open" protocols (which are ultimately controlled by a single entity and never standardized).
To be fair, IETF standardization of XMPP was somewhat afterthought, and further extensions (XEPs), which are necessary for modern clients, are not IETF standardized.
Standardizing the core concepts + the extensibility of XMPP was absolutely necessary to achieve the necessary protocol agility I think. Requirements have changed a LOT since 1998 and we still have innovative and modern XMPP clients, maintained by the community, mostly in their free time without any need for millions of dollars of VC money.
Without standardization, there can be no interoperability and without agility any IM protocol will soon be outdated. I think XMPP is a success story because it realized this, but it's a success story that isn't told very often.
And fruit s few years after that they stop had a page about their commitment to open messaging standards and federation... They finally took that down.
