Here's why:

* Chloroplasts contain chlorophyll: This green pigment is essential for absorbing light energy from the sun, which is the first step in photosynthesis.

* Chloroplasts have a unique structure: They have a double membrane system, including thylakoid membranes that are stacked into grana, where light-dependent reactions occur. The stroma, the fluid surrounding the thylakoids, is where the light-independent reactions (Calvin cycle) take place.

While other organelles like the nucleus (for DNA) and mitochondria (for energy production) play supporting roles, the chloroplast is the central player in photosynthesis.