Well, according to author Jennifer McLagan, it's because we don't eat enough of it! She expounds on this argument in her book, Fat: An Appreciation of a Misunderstood Ingredient, With Recipes.
I say, it's about time we started returning to old-fashioned ways of thinking about our vittels! By now, we're familiar with the mantra: More home-cooked meals with natural, unprocessed ingredients; smaller servings of tasty, well-balanced meals of proteins, carbs and fats; more fruits, veggies and whole grains in the overall diet; moderation in alcohol, processed foods, desserts. Yada, yada, yada.
But dietitians have steered pretty clear of suggesting that -- horrors!! -- we eat more saturated fats that come from animals as opposed to plants (the exaltation of olive oil as a magic ingredient comes to mind!). So, it's refreshing to hear someone not only make this claim, but also support it with an entire book!
You don't necessarily have to read her book in order to grasp her argument, or come around to her way of thinking. Here's a good interview in Salon that helps explain the theory.
Read it, and then go and eat a steak. Without guilt!!!