Why is the Dark Reaction sometimes called Light Independent Reaction?

Answer 1

Because the dark reactions are CO2 assimilation's and do not need light energy. They use the ATP and NADPH created from the light reactions to convert CO2 to carbohydrates, so this can happen in the "dark" as long as the light reactions already happened.

Answer 2

The Dark Reaction is sometimes called the Light Independent Reaction because it can occur without the presence of light. It takes place in the stroma of the chloroplasts and is driven by the products of the Light Reaction, such as ATP and NADPH. While the Light Reaction requires light to generate these products, the Dark Reaction can proceed independently once these molecules are available.