It does, actually. i think they are arranged this way to
optimise coverage, which means attacks from the side as well.
Especially when u consider anti-ship missiles typically hit the
side of a ship where the area is larger. So, if a missile
approaches from the side, u'd swing them around, and u'd have two
launchers to cover each side, since it's unlikely to be attacked by
two missiles from both sides at the same time. By the same logic,
since the target area from the rear isn't so large, i guess u would
need only one to cover. I could be mistaken, of course. 
