a. to repair tissue. Tissue is a term that describes a group of cells, all of which are the same or similar cell type, which collectively perform a role in a multicellular organism which can only be done, or can only be done efficiently, when all of those cells are aggregated in the form of that tissue structure. Examples of tissue include skin and muscle. When these structures are damaged, this typically involves cells being killed, destroyed, or removed from the body entirely. All of these create gaps where those cells once were, reducing the effectiveness of the tissue and requiring cell division from the remaining cells to bridge the gap.
Protein production might increase as a result of cells dividing, but this is not the primary purpose. This is like saying the primary purpose of having babies is to increase the number of people in college.
Total energy use would also increase as a result of cells dividing, but this, too, is like saying the purpose of having babies is to use more electricity.
Likewise, cells dividing would probably help the organism to obtain more food, but this is an outcome of cell division, not the primary purpose.