What part of the cell theory explains why organisme grow?

The third part of the cell theory surely explains how organisms grow, but unfortunately not why. It says that every living cell originates as a result of the division of a preexisting cell and no cell can spontaneously self-assemble as it was believed till the middle of the 19th century according to the anomalous generation theory.

It's either -limiting factors or -scarce resources but i'd go with my first answer since the food and water are abundant they really aren't scarce