Because I think it'd be nice to be able to chat without having to close the window, then open it again, then close it to see/reply to messages, when we can just chat freely even with the window open. Or at least be able to see what people are saying so you dont have to hunt for the last message you read when you close the window.
Or maybe im just nit-picking. idk. Thoughts?
Depends on your resolution; the Mission interface doesn't block it on mine. Aside from that, yeah, would be nice for the good chunk of people who don't have huge resolutions.