
So...why can't I just go standby?
Many customers would like for us to waive the "standby upgrade," the difference in fare we collect when a customer holding a discounted ticket wants to take an earlier flight. Because Southwest employees are known for "bending" the rules in customers favor, our adherence to this one is often perceived as an "exception the exception."
To illustrate why our customers flexibility exempts this policy, I'd like to share with you some inside history of the business. Long ago, there was only one ticket, called full (or walk-up) fare. However, there weren't always enough full fare customers to fill up the frequent flights they wanted to choose from.Yet, to lower the fare enough to sell all those seats would mean losing money on nearly every trip!
So restricted fares were born, making air travel affordable to more people than ever. However, Southwest did not raise full fares to make this discounting possible. We simply lowered prices on a limited number of seats per plane, adding restrictions acceptable to customers who could plan their travel well in advance.
Presently, under this arrangement, everyone benefits. The full-fare customer can stand by or change reservations among a wider selection of flights, with transaction costs already built into the fare. The bargain traveler is able to fly (rather than drive), and can still change plans by adapting to new restrictions, or by becoming a full-fare customer - typically paying less than our competitors walk-up fares.
Full-fare privileges at full-fare prices. Restrictions at discounted prices. It is really nothing new: Movie theaters have has matinee specials for decades. However, they don't accept matinee tickets at Saturday-night shows. Neither do we allow discounted, restricted tickets to be used like full-fare tickets.
But what about Southwest vaunted flexibility toward our customers? Unfortunately, exceptions to this particular rule would have a way of becoming habit, habit of becoming norm, and in short order, no one would see any reason to buy a full-fare ticket. We would then have to raise discounted fares to make up for lost revenue, pricing the budget traveler out of the airplane and scrapping the mutually beneficial relationship between the bargain and business traveler. Without sky-high first class and walk-up fares (like our rivals!) to compensate, Southwest Airlines would no longer mean lower fares for everyone.
Of course, our employees still have the flexibility to help customers in verifiable dire circumstances. Normally, however, the agreement we make with customers at the time of ticket purchase should be kept - on both ends. It is the only way to be fair to the full-fare customer and still offer the low fares and high flight frequency people enjoy when Southwest serves their hometown.
-Herb Kelleher
There you have it folks!!!!! That's the official reason and answer for your questions!

SWA TPA