The purpose of a conclusion is not a rote reiteration of the thesis and your arguments. A recap may help tie all your arguments together for the audience, especially in a long paper, but it is not enough. Just as you needed to interpret quoted material to ensure that your readers understood it the way you wanted them to, you need to interpret your arguments at the end of a paper to ensure that the audience will understand them in the same broader context that you do.
Ultimately, you want the conclusion to give your readers something extra to think about. And you want your own thoughts to stick with them long after they have finished reading the paper.
