Sugar, fat and salt are greatly stimulating your appetite (even if you do get all your minerals and vitamins and so on). That's why people can usually always eat a small dessert even if they feel already full.
People are also creatures of habit, if there is no high calorie snack at hand in the fridge then people won't eat it impulsively. In turn when people do get hungry there should be something with more complex carbs at hand to eat.
It's natural that we enjoy sugar, fat and salt, that's what a healthy body does but the habitat we live in is not the habitat where those qualities evolved and provided health. Changing the habitat, the contents of the fridge for example, goes a long way.