It's about comfort, not cost. Mileage runs are generally done for status. Air travel is miserable, and the extra perks that come with status are almost priceles

It's about comfort, not cost. Mileage runs are generally done for status. Air travel is miserable, and the extra perks that come with status are almost priceless. Also, there's another huge benefit to sticking with a single airline - you learn that airline. When I used to fly 2 weekends/month, it was very disconcerting when I had to use a non-United airline and deal with the subtly to vastly different quirks.