Well hey, if Muse has the time to include it and feels like it, I don't see why not. Other than that, it's nothing you can't get by saying "Hello, I have music on, so if you want something, text me."
Most of the time I actually have music on myself, and I still win about 80% of my games. It's a matter of knowing what you're doing. About the afk, same thing, you can usually guess when someone has decided to alt tab to look at lolcats and is just not here, or is faking to be alt tabbed looking at lolcats so he can bring whatever he feels like rather than what he needs.
TL;DR: They wouldn't do that, because it's a little redundant when you can just say that you have music on, and people can guess that you're AFK.