@Visibility3Miles
Charging extra for checked luggage (as well as hassle from lost or pilfered luggage) begs people to carry-on everything they can.
During the liquid bomb panic when only a ziploc bag of essentials was allowed it was amazing how fast turn arounds were. A 76 loaded from start to finish inside 15 minutes. Now there will always be people that want their carry on with them. But there are also many who (trusting souls) are happy to check all their stuff.
I wonder if any of the beancounters have done a cost benefit analysis against delayed turnarounds with 30-40 minutes to load SLF compared to slick 20 minute turnarounds (and a correct weight and balance). I would not be surprised if the charges for checked bags don't come close to paying for the inefficiency that carry-ons cause. But the cost is in a different budget so the beancounter still gets his bonus.