Here's why:

* Surface area to volume ratio: As a cell grows, its volume increases faster than its surface area. This means the cell's surface area (its membrane) can't keep up with the demands of the increasing volume. This limits the amount of nutrients that can enter the cell and the amount of waste that can exit.

* Inefficient transport: Smaller cells are more efficient at transporting materials across their membrane. Large cells struggle to get nutrients in and waste out quickly enough.

* DNA overload: The cell's DNA needs to control all the activities within the cell. If a cell gets too big, its DNA can't effectively manage the increasing demands.

Cell division solves these problems by creating smaller cells with a higher surface area to volume ratio, improving transport efficiency, and ensuring adequate DNA control.