In your own words, explain why the keratinocytes do not produce melanin?

Melanocytes produce Melanin. Keratinocytes assist in this function.

Explanation:

Keratinocytes contribute to protecting the body from ultraviolet radiation (UVR) by taking up melanosomes, vesicles containing the endogenous photoprotectant melanin, from epidermal melanocytes. Each melanocyte in the epidermis has several dendrites that stretch out to connect it with many keratinocytes. The melanin is then stored within keratinocytes and melanocytes in the perinuclear area as supranuclear “caps”, where it protects the DNA from UVR-induced damage.

Simply because most( 90%) keratnocytes (superficial keratinocytes) are keratinalized, without nucleus. They are  mostly dead cells with  cytoplasm   made up of mostly keratin ;which is more   protein  than cells.

Melanin is produced by melanocytes but  Keratinocytes lacks melanocytes.

Thus Keratinocyte with no nucleus,  with dead cells,with cytoplasm of  keratin, and most importantly   with no melanin secreting cells  of  melanocytes  can not  produce melanin.

Explanation:

b.have there own function.