conversion from RGB to LAB color space, most of the authors consider only L-image for further processing. why?

conversion from RGB to LAB color space, most of the authors consider only L(X)-image (luminant component) for further processing. why? why not other two images(components) a(y,Z) and b(x,Z)?

Answer 1

[Image Analyst]

Perhaps they don't need them.

Whether you do or not depends on your image. Post it if you want advice.

[Walter Roberson]

The image alone is not sufficient: we have to know what you need to do with the image.