In fallout 3 you got a variety of meat but when you ate it, it didn't appear you cooked it. Do you think there should be the ability to cook food to give it bonuses (like no rads) and maybe in hardcoe mode you'd need to cook it to eat it? And now that I think about you just ate blamco mac&cheese right outta the box!
That Blamco Mac 'n' Cheese was also 200 years old, I doubt cooking it would make it any more edible. Yuck!
But I agree that you should be able to cook raw food, and there should be less pre-war food aswell. Eating cooked food should be better to your health.