> While I kinda get removing it from the mobile app, I don't really know what the rationale is for getting rid of mobile web chat though. It's not like it's disappearing from the desktop web app anytime soon, right?

I'm guessing that within the next one year or so, Facebook will force people to move to official apps even on desktop systems (like Windows and OS X), closing browser based access completely. That would give Facebook more control on tracking, ads, etc.