Well… I can answer for Paul here… why NOT?
If your audio is not positional… there is absolutely no reason to attach it to the scene graph.
Okay, but why wouldn’t you attach the positional ones?
I’m not sure that was what Paul meant… but if he did I’ll let him answer 
Because they aren’t rendered and I position them in world locations (I have an ES after all). There is no benefit to attaching them and only a little extra hassle.