Here's why:

* Glucose, a simple sugar, is the primary fuel for cellular respiration. This process breaks down glucose to produce ATP, the energy currency of the cell.

* Other carbohydrates, like starch and glycogen, can be broken down into glucose for energy. Starch is the storage form of carbohydrates in plants, while glycogen is the storage form in animals.

* Carbohydrates are readily available and relatively easy to break down, making them efficient energy sources.

While fats and proteins can also be used for energy, carbohydrates are the preferred source due to their efficiency and abundance.