Well most of the times Ive seen this its during a mad furball. I think few jump in the middle of a fight, especially a 1 on 1 fight without asking if they need help first.
In a furball anything can happen...between the sheer number of icons darting around and framerate drop, it makes SA harder and most times you want red, dead, sooner than later. And that leads to issues like what we've discussed.
It happens to me, and I probably do it to others...just bite your tongue and get on with it. Screaming at someone on range isnt gonna help anything.