For me, it would be because I avoid sulfates. My hair tends to run dry, and that sulfate would be no friend to me.
Have you investigated going sulfate free or using the cg method? It can really help to address the dryness that can come with curly hair, and it can work well to being out the curl pattern.
gives an overview of the cg method. There is also a poo-less forum that can help. You can also ask here.
For some visual proof of what going mostly silicone and sulfate free can do for you, check this