Maybe it was a weight decision. Rather than add wires, use the ones that are already there. It may sound ludicrous, but weight (and therefore fuel and range) is

Maybe it was a weight decision. Rather than add wires, use the ones that are already there. It may sound ludicrous, but weight (and therefore fuel and range) is almost a cult in airliner manufacturing, and for good reason. One item saved isn't much, but if you're diligent you get a lot of items saved, and they add up in total.