Raison d'Être des Quale

If you define quale (qualia) to be the sense data given to conscious scrutiny, then it may be easy to tell why such things exist.  Sometimes the brain would need to go back sense data to check if something goes wrong in detail.  This qualia business is carried out in early sensory cortices.  If these cortices are destroyed, not only perception but also the ability of forming images vanishes (Damasio, Descartes' Error, p. 99).  The consciousness is the sequential cognitive process integrating all quale (=sense data) for planning actions.  This is, of course, a functional explanation and does not answer the question whether qualia-free zombies exist...