Narrative and matched play are not so easily separated from each other - it's more of a sliding scale. In many instances narrative gaming uses the points system as a way of creating roughly equal sides, then layering the narrative aspects on top. It is easier and more helpful to give Mercenaries, and allies, a space within the matched play points system as this will lend legitimacy to, and encourage, their use within narrative gaming. At the same time, they have to ensure that allies, and now mercenaries, do not unbalance the purely matched, tournament-style, play end of the scale. The end result effectively is that allies, and mercenaries hopefully, are generally optional but not game-breaking, though some older armies that lack particular types of unit may benefit more (which is fair enough). I think, on the whole, that GW has kept the balance pretty well in this instance.