Here's why:

* Chlorophyll is responsible for absorbing light energy, particularly in the red and blue wavelengths, and converting it into chemical energy during photosynthesis.

* Carotenoids are also present in plants and contribute to photosynthesis, but they primarily absorb light in the blue and green wavelengths. They act as accessory pigments and can also protect chlorophyll from damage.

* Anthocyanins are pigments responsible for the red, purple, and blue colors in many plants, but they are not directly involved in photosynthesis.

Therefore, chlorophyll is the primary photosynthetic pigment in plants.