You are arguing that a $600+ phone for yourself and all your friends is more "readily available to consumers" than a $0 downloadable open source open standard software with multiple clients available? Two-thirds of the world population live on less than $10 a day. You are living in quite the bubble. XMPP is way more "readily available to consumers" on world average.

Gtalk was polished enough. It didn't have OTR built in, but majority of users don't really need end to end encryption anyway, it only makes their life not good.

Also, iMessage never reached a level of polish to work on anything not produced by Apple. If we're taking proprietary vendor specific secure services, Blackberry did it before Apple, too. So, definitely not the first and not the only.

When you control your own server you kinda don't really need end to end encryption. It only enhances security when you don't trust the entity delivering your messages. It also degrades UX considerably: if the server does not know the contents of your message, it can't do server side archive search, you can't sync devices easily, etc.