The reason airlines are charging bag fees is because they have to pay a tax as a percentage of each ticket sold, but the tax does not apply to fees for things like bags and in-flight service. So the airlines are shifting as many costs as possible to untaxed fees and away from the ticket price.
Congress made this mess when they passed this poorly drafted tax law. Now they blame the airlines, and demand more authority to clean up the mess they, themselves, made. Typical.
Typical of all their Ponzi schemes. The more control the government takes, the worse things get.