Did you know that men have 9 holes in their bodies and women have 10? These can be categorized into senses (eyes, ears, nose), reproduction (as you can guess), elimination, and food intake (mouth). That's it. The body protects itself so much that it has specific reasons for holes. There is only one hole that is intended for things to fully enter the body and be utilized by the body: the mouth.
It is a protective issue because whatever enters the body can enter for harm or for good. Foods that we eat become part of us. They are building blocks of our bodies whether we are still growing or not. Do you want to build your body with foods that major companies want to sell you or with what your body was hoping to receive? The body is intelligent; it will use whatever we eat to the best of its ability to build and repair. Matter has limitations, and the body cannot use essential nutrients that are not there or are not in an available state for utilization.
But that's just IMO