Here's why:

* Chlorophyll is the primary pigment responsible for photosynthesis. It absorbs light energy, specifically in the blue and red wavelengths, while reflecting green light (which is why plants appear green).

* This absorbed light energy is then used to power the chemical reactions of photosynthesis, where carbon dioxide and water are converted into glucose (sugar) and oxygen.

While other pigments like carotenoids and anthocyanins can also absorb light energy, they play secondary roles in photosynthesis or are involved in other functions like attracting pollinators or protecting the plant from damage.