The problem for all airlines is that the number one consideration is price, absent a corporate requirement to fly a specific airline. This was a little while back. I was waiting for my son at school and got to talking to the mother of one of his classmates. Her husband is a UA mechanic. With a family of five, it's really hard to fly non-rev at any time that is popular for travel, such as spring break on the weekends. Planes are simply too full. But, when they went to book tickets to Florida, they found that AA was $50 a ticket cheaper. For a family of five, that's $250. That could very pay pay for the rental car.
So, when a UA employee flies AA because of the price, that really shows that price is the number one factor.
In the days of regulation, people picked airlines because of a variety of factors. My father avoided Eastern like the plague, because so many flights were late. He liked Delta morning flights, because its breakfast were southern, often with grits. When his salary grade permitted him to fly F, he flew Braniff whenever possible, because dinner often meant cherries jubilee for dessert.
These days, about the only time people choose based on the soft and hard product are for flights to Europe, Asia, or Latin America, if you can fly J or F.
A lot of people think of air travel as a commodity, like milk, gasoline, or canned vegetables. By the same token, I've known people who swore of one of the legacies. Then, the new favorite legacy merged, and service went south. Then, the next legacy screwed up. One friend of mine basically tells me that he's come to the conclusion that all U.S. carriers are crummy, even Southwest, since their advance-purchase fares aren't the bargain that they were 10 or 20 years ago.
Knowing that trains aren't a realistic option, outside of the northeast, and that cars can't compete much beyond 250 miles or so, airlines know that they are the only game in town for travel.