Here's why:

* Chloroplasts are the organelles specifically designed for photosynthesis.

* They contain the green pigment chlorophyll, which captures light energy from the sun.

* They also have internal membranes called thylakoids that are stacked into grana, where the light-dependent reactions of photosynthesis occur.

* The space between the thylakoids and the outer membrane of the chloroplast is called the stroma, where the light-independent reactions (Calvin cycle) take place.

So, while other parts of the cell are involved in processes related to photosynthesis, the chloroplast is the primary site where the entire process of photosynthesis takes place.