The dividing lines on weight for the backpacking crowd were not arbitrary. They came from trying to grind out all excess weight. Then new materials and efforts were expended and SUL became possible. To base our needs on what airlines (which ones) do, is arbitrary. They keep moving the bar. Also, many people do not fly for their trips, so it is irrelevant to them. And it relieves pressure to go beyond airline established numbers once they are reached. Anyone who wants to use various levels and packing lists to prepare for a trip were they fly should have no difficulty.