I love XMPP, but its OTR plugin is kind of glitchy.
Businesses want to analyze internal company messages. Chat protocols / platforms need to make inroads with one of the core audiences for online chat. Those are largely taken right now, (slack/teams business, discord gaming/oss). If it is personal/small group messaging, several E2EE options already exist, though I understand Jabber/XMPP is trying to be in the chatroom genre
The way businesses handle this is by installing a certificate they manage and deploy to their proxies.
chat is network effect, so a chat app needs to answer "which network of people" if the creators about traction?
I can easily imagine a future where people switch between three messengers, one for general communications with acquaintances and family, one for work, and one for their social circle. Many already do this with social networks.
I would rather want a feature, like Telegram has, where you can set auto-delete of all messages older than N days.
Everyone who has to, say, prove that they kept paying their rent for a year without interruptions. You sent a photo of your money transfer from the bank app to your landlord, and he sends the "received" screenshot from his bank app.
Moreover, a lot (even most) people make personal notes by sending messages to themselves.
Most people trust the police. This might not be justified in your state, but most people still do.
"Where were you during the event X? I was very far from the place you are interested in, as can be proven by this photo, sent to my grandma, have a look at the history in her phone."
If message history is important it should be backed up on the receiver's end after decryption, like WhatsApp and signal do.