The discussion was solely about baggage fees and not passenger weight, unless you also want a pax "weigh-in" at check in. In addition to the fuel cost, extra bags also put a strain on the baggage handling system in terms of loading the plane to get an on time departure (whenever that happens) and afterwards getting them to the luggage carousel after the flight in a timely manner so the pax aren't screaming because they're still "waiting" for their luggage. I guess you could weigh pax if you wanted to but you and I know that isn't going to happen . The path of least resistance for the airlines is to simply charge for the extra bags. Also, I'm sure you would agree that if you and I weigh the exact same and you have 4 bags and I only have a carry-on, you are costing the airline more to fly you. The philosophy seems to be no matter a pax weighs, a seat is a seat, and the way to cover extra fuel costs for extra weight is to charge bag fees and avoid the pax "weigh-in". I don't disagree with them. Can you imagine check in, "please take off your shoes and step on the scales, sir".