Why has there been no major innovations in messaging platforms?

It seems like messaging apps have been the same for the past couple years. Images, GIFs and stickers exist on all platforms and the major differentiators between popular messaging apps are the networks that use them. Telegram, Signal, WhatsApp, Messenger are all practically the same platform just with different demographics. Are there reasons that this sector has yet to have major innovation? Google Allo was the closest thing to the next generation of messaging apps I've seen but UI and UX were very poor and the google Assistant was off putting.

IMO iMessage is the closest to what Allo could have been with Siri integration. Apple (as usual) is taking baby steps with said integration but I don't see a viable candidate. I would've though AI would play a major role in texting given it's become a very dynamic medium of communication relative to voice/video/email (which is a more formal derivative of text).

Thoughts?