There is a pretty obvious reason that the Pittsburgh Steelers felt the need to bring Vance McDonald into their tight end equation, and that is quite simply that he offers things that he brings some qualities to the table that the rest of their group currently on the roster does not.
One of those qualities that he brings that the other tight ends on the roster have not been able to do consistently is present a vertical threat. While he is by no means one of those glorified wide receiver type tight ends, he is more than capable of going down the field, and this is something the Steelers showed obvious interest in last season.