They are only fortified with a couple of vitamins that society has decided is the most important for not causing the whole population to end up with scurvy. If

They are only fortified with a couple of vitamins that society has decided is the most important for not causing the whole population to end up with scurvy. If you eat a balanced diet, you will eat a random selection of everything. All things contain different nutrients that are important for us and since we don't know exactly which ones, we say balanced diet when we mean everything.