Here's why:

* Versatile: Glucose can be broken down through cellular respiration to produce ATP, the primary energy currency of cells.

* Abundant: Glucose is readily available from the foods we eat (carbohydrates) and can be stored in the body as glycogen.

* Efficient: Glucose is a relatively efficient fuel source, providing a good amount of energy per molecule.

While other molecules like fatty acids can also be used for energy, glucose is the primary fuel source for most cells in the body.