Though the shell has no inherent value, its presence is indispensable. Man's feelings and emotions are always temporary. Though at times of spiritual highs we are convinced of our righteousness, a religiousity anchored in emotion is destined to fade. As uplifting feelings recede, man has no physical basis by which to sustain his commitment. There is no guarantee that he will actually execute the will of G-d.
Angels never hesitate.
Angels are G-d's loyal and trusted agents, dedicated to proper performance. They are messengers, every fiber of their being identifiying with the present mission, hence, they don't delay. For the same reason, they carry out only one function at a time. When the B'nai Yisrael promised to do whatever G-d commands, irregardless of the difficulty, they successfully imitated the Malachim, willing to perform at a level beyond normal human capacity. Actions then, have a value of their own, as man relates to a dimension where G-d's will is clear and unquestioned.