A rather easy travel decision

I am thinking about attending a one-day planning seminar in Chicago in mid-November. I did some research and discovered the following:

• I can fly Southwest non-stop from Houston Hobby to Chicago Midway for $372 round-trip, or...

• I can fly United non-stop from Houston Bush Intercontinental to Chicago O'Hare for $1,042 round-trip.

(American Airlines also flies between Bush Intercontinental and O'Hare. Their price was the same as United's. American, United and Southwest are the only three airlines which fly between the nation's third- and fourth-largest cities without requiring connections.)

Given that Hobby is the closer airport to where I live, Southwest (unlike United) doesn't charge a checked bag fee, drinks are $2 cheaper on Southwest, and it doesn't matter which Chicago airport I use because it's easy to get to downtown (where the seminar is) from either airport using the 'L', this is obviously a no-brainer.

Why is United charging almost three times as much as Southwest for a flight between, airports aside, the same city pair? Obviously, they think they can get away with it. Maybe they think their customer base is loyal enough, or prefers Intercontinental/O'Hare over Hobby/Midway enough, or disdains flying on Southwest enough, that they'll pay the extra cost.

Or, maybe it's just another reason why, as far as I'm concerned, Southwest is an exponentially better airline than United.