Why do airlines charge passengers to check bags?

I know the country is gripped with the biggest wave of Populism since the early 20th century, but I'm sitting in the Atlanta airport half pissed off because I had to check my bag. It's a backpack, and there was nothing that I needed in the bag for the next leg of my journey (ATL to DC). HOWEVER, backpacks should not have to be checked. They're small and flexible. But since I was one of the last people on the plane, there was no room in the cabin above the seats... and my bag is somewhere in Atlanta.

Enough of my bitching... let's get to the point. Why do airlines charge for passengers checking bags? It seems to me that it would make more sense for airlines to charge for any bag that is not checked. The reasoning is simple.

Airlines can cut costs if they turn the plane around quickly. This cuts down on all sorts of costs--the faster an airline can get the people off the plane, do a quick clean, and then get the next group of passengers on the plane allows them to fly more flights with the same plane, which could possibly eliminate airplanes entirely.

But when passengers bring bags--especially those hard cover, one person weekend getaway type rollers--on to the plane, they store them in the overhead. And it takes forever for people to get those things into the overhead bins and it takes them even longer to get them down and off the plane. Don't believe me? Fly on an international flight sometime. On those flights it seems like they can unload a Boeing 777 or 747 in about five minutes. Yet a Boeing 737 takes about ten minutes to unload.

But airlines give passengers every incentive in the world to not check their bags. Wouldn't airlines be better off to have passengers waiting for their bags at a claim then to have hundreds of people waiting either on the plate or at the gate? Why not charge passages five bucks for ever hard covered, rolling bag? Sure passangers are going to complain because the airline "always loses their bag" (simply not true). Really they're just upset about waiting for their bags (yet anyone who's sat in the bag of a plane knows, by the time one gets off the back of a plane and walks to the baggage claim the bags are there).

It would be a simple system. If you have a bag that is 12" by 24" (or 14" by 28" whatever it is), you can check your bag for free or pay a five dollar fee. If the airline loses your bag, you can claim ten bucks for the inconvenience (and honestly, they could give you twenty bucks because not that many bags are lost so they'd easily make the $20 from people paying to not check their bags). Planes deboard and board quicker... everyone wins. Save the white business guy who is on his cell phone the up until the second the plane takes off. You know that guy. He probably sells insurance. And he isn't that big of a deal because he's sitting coach. But he wants you to think he is. [Editor's note, TPB went on for about 100 words more, but I cut that; END]