Because of the single word "artery clogging saturate fat" myth that Ancel Keys helped to start with his "7 countries study" that was conducted a long time ago, before even the different types of cholesterol where mapped...
What he actually found in terms of what the USA has issues with was sugar(Sucrose - Fructose and Glucose), the stuff you find in soda and quite a lot of other products in the US today, not that you are alone anymore on this mistake.
We need to move on people, and realize that the stuff that is killing us and created the obesity epidemic in the first place was simple and refined carbohydrates, not dietary fat.
Sugar: The Bitter Truth by Robert Lustig M.D.
http://www.youtube.com/watch?v=dBnniua6-oM
Same talk, but updated.
http://www.youtube.com/watch?v=kOCPyheVesM
Enjoy Eating Saturated Fats: They're Good for You. Donald W. Miller, Jr., M.D.
http://www.youtube.com/watch?v=vRe9z32NZHY
Gary Taubes(Journalist, not an M.D.): What If Fat, Doesn't Make You Fat? (Dr Dean Ornish isen't entirely convinced about fat, so it's an interesting counter argument.)
http://www.youtube.com/watch?v=HCgTlC8PE0Q
This seems to be a decent blog about the subject as well, by Peter Attia M.D.:
http://eatingacademy.com/
It's all about how much carbohydrates you eat and what kind.

