Accuracy of Looks Previews

I have a question regrding the “Looks” category: I am not sure of its purpose…sometimes the colors on the looks previews are not the same as the processed colors, and in a few cases the applied textures actually block part of the processed image. I thought the purpose of “Looks” was to help find a look that complements your image. If the looks previews are not predictable, why have them?