If you think that airlines are nickle and diming you with fees, that's because they are. Airlines contend that the majority of these fees are for extraneous stuff not essential for travel. Like, for instance, luggage.
Indeed, when questioned by Congress, Spirit Airlines CEO Ben Baldanza defended his company's fees:
The head of the nation's most fee-happy airline told Congress today that bringing luggage on vacation was "not essential" to travel and his airline was actually helping the poor fly by charging up to $45 to place a carry-on bag in the overhead bin.
"We are certain that Spirit's decision to unbundle services not essential to the transportation of passengers, has enabled more passengers to fly at lower cost," said Spirit Airlines CEO Ben Baldanza. "Indeed given our low fares, it has allowed many to travel who otherwise simply could not afford to do so."