I am not totally sure it is just the greed of the carriers though, looking to book internal flights in the Uk I was quite amazed at how high a proportion of the fare was 'taxes' on top of which the airport itself added a '£5 airport development fee' to be paid by each passenger before security.
personally i think the whole business model is wrong when the airlines are relying on the various 'extras' to generate profit and creating so much customer bad feeling. Is this however partly due to a government that is always looking for the next thing it can 'tax to the hilt' and a paying public who are now desperate to make their hard earned cash go further.