American Airlines Bag Charge Too Much

Would that be for a carry on bag as well? My opinion in general on these things is that in ye olden days you were allowed baggage up to xxxx amount of lbs/kg per person per flight. If you were over you'd pay a charge. That seems reasonable because when they weigh everybody's stuff and tally it up, then the Airline will know how much extra fuel they will need. I'm guessing that one or the other of the follwing possibilities is behind this charge. a) they got a really cool contract to transport something in their passenger planes and want their paying passengers to keep their bags to a minimum. b) the people who travel on AA are getting more and more obese and they don't want to charge them for the extra weight but do need to find a non-discriminatory way of taxing the passengers. c) fuel is getting more expensive for them as well. Charging a little extra for a bag would help them to be able to pay for the fuel.