Here's why:

* Interphase is the period of growth and preparation for cell division. It's the longest part of the cell cycle, encompassing about 90% of the total time.

* M phase (mitosis or meiosis) is the actual process of cell division and is relatively short compared to interphase.

During interphase, the cell performs essential functions like:

* G1 phase: Cell growth and normal metabolic activities.

* S phase: DNA replication.

* G2 phase: More cell growth and preparation for mitosis.

While mitosis is crucial for growth and development, interphase is where the cell spends most of its time carrying out its normal activities and preparing for division.