Why do you add soluble starch to nutrient agar rather than just growing cultures on potatoes?

Soluble starch is added to nutrient agar to provide a consistent and easily controlled source of carbohydrates for microbial growth, allowing for standardized experiments. Unlike potatoes, which can vary in nutrient composition and may contain inhibitory compounds, nutrient agar with soluble starch ensures uniformity and reproducibility. This also allows for the cultivation of a wider range of microorganisms in a more sterile environment.