In 1987, when I was 11 years old, I started flying United because my parents decided to fly United to Asia for our family vacation that year.
Today, I still fly United because:
The route network is expansive. I can get just about anywhere in the world I want to go on United. And the few other places I can get to on Star Alliance partners.
The maintenance and engineering staff are the best in the world. An airline that is as deeply involved with the design and testing of a completely new aircraft, namely the 777, is truly ahead of the pack.
The fleet consists of airplanes that I prefer to fly. Yes, even the A320 and A319's, despite my Boeing bias.
The expedient and courteous nature of the service, on almost all occasions, is outstanding. Yes, it's gotten better as I've "climbed" the elite ranks, but it was never bad. Now, as a 1K, being treated like royalty on a few occasions here and there, I don't see any reason to go anywhere else.
O'Hare is my favorite airport, and Chicago is my hometown. Even if I'm just passing through, I still like to see it every week or two.
"Rhapsody in Blue" is one of my favorite musical pieces. I like having it pounded through my head on a continual basis...
And finally, I've gotten to know the ins and outs of every aspect of United and the Mileage Plus program... I can find my way through ORD Terminal 1 with a blindfold... I know exactly which seats I want on each type of aircraft... I know some of the personnel... and I know how to maximize my miles... it would take years to figure all that out again with another airline!