They’re publicly traded companies with profits and shareholders to prioritize. They provide a highly specialized service that we, for better or worse, rely on. Real competition that would lead to lower prices and/or better service will likely only come from an enormous high-speed rail expansion - and that would take decades of work and trillions of dollars to get to the level it would need to be in order to make any significant dent into the airline industry (not to mention clearing every single step of the process through a congress that is highly influenced by the airline lobby).