The Southwest board may not be the most productive site for answering your question, given that WN is a single class, open seating airline.

For fun, I'll turn this around for you. Why would someone buy a Mercedes or other luxury car when a VW or Chevrolet will get them to their destination at the same time? Maybe the answer is comfort, nice additional features, more attentive service and a feeling of some exclusivity.

Road warriors scramble for free upgrades to first class on legacy carriers so they can enjoy the extra space and comfort of first class at a coach price.

(this post moved to TravelBuzz from Southwest Rapid Rewards)