Why I don't believe in "win-loss" analysis for salespeople:
The car section of tomorrow's New York Times features a review of the new Pontiac Solstice. The reviewer compares this convertible to its closest competitor, the Mazda Miata. He finds that the Miata is faster, lighter, better equipped, more ergonomic inside, with an easier to use convertible top and better gas mileage.
He then goes on to rave about the obviously (by the numbers) inferior Solstice.
For the same reason you've ever lost any sale your organization has ever been up for.
Because the customer liked someone else better.