Well, I think what RJSlow said applies as to some of the reasons why not.

My feelings: Yeah, it would be nice to be able to tell someone their formation is bad, or say good game.. which you can do already if you are FB friends. It's the not nice parts. Having played "social" games and on other platforms, I usually look for a way to turn the chat off. I don't appreciate trash talking, being harrassed, and the distraction of it. If there was chat on T11.. I would still be looking for a way to turn it off.