Here's why:

* Growth: Mitosis is the process of cell division that creates two identical daughter cells from one parent cell. This is essential for the growth and development of an organism from a single fertilized egg.

* Repair and Renewal: Mitosis is also used to replace damaged or worn-out cells. This is crucial for maintaining the health and function of tissues and organs.

Even single-celled animals, like amoebas, use mitosis to reproduce.

Let me know if you have any other questions!