Measuring is important in cooking and baking. The best of chefs often season without measuring and create new dishes without a recipe, but they learned to cook by following the measurements in recipes.
Measuring is especially important when baking. Because recipes like breads, dough, batter and the like are basically chemistry, small variations in the amount of oil, butter, baking powder or other ingredient can ruin a recipe.
Measuring is one of the single most important techniques in cooking healthy. This is due to the fact that by using the correct amount of ingredients, you know exactly how much fat and calories you are eating.