Well, and Zappos' risk ceiling is incredibly low, with high margins to enable fantastic service. With an airline you're talking about hundreds or thousands of dollars at risk in each customer service occurrence, and terrible margins.

Part of this is just how the market works: if you want to fly on a jet airplane across a continent for a couple hundred bucks, expect a McDonald's level of competency. Airlines are in a perpetual race to the bottom, and the result is cheap travel at the cost of customer service.