Here's why:

* Interphase is the period of growth and normal activity for a cell. It's when the cell performs its functions, produces proteins, and prepares for division.

* Mitosis (cell division) is a relatively short process compared to interphase. It's the process where a single cell divides into two identical daughter cells.

While the specific length of interphase varies between cell types and organisms, it generally accounts for the majority of a cell's lifespan.