Because its less convenient than what I have. I tend to respond to messages as a side effect of using the newsfeed feature. I do not use Facebook messaging enough on its own to warrant another messaging app outside gchat and SMS. Removing the feature from the main Facebook app only ensures I'll use Gchat more. Dumb move on Facebook's part, at least for my user profile.

I imagine they are doing this because they don't see the point in supporting both code bases.

Is your phone really that memory constrained? Why not just download it?

I have a note 2. I use messaging because it's attached to my news feed. Remove the convenience and it's no different from the 5 other messaging apps i have.

I see, makes sense. I had made the assumption you had friends that exclusively used facebook messenger.