Tennyson doesn't write "The Charge of the Light Brigade" because it's a good story, or because he just thinks you'd be kind of interested. He wants to accomplish something specific. He wants the memory of the anonymous men of the Light Brigade to live forever. You know what? It worked. We guarantee that you would never have heard about the Light Brigade in the Crimean War if it weren't for this poem, and now you're part of the tradition of remembering these men.
Tennyson's poem carefully balances his respect for the Light Brigade with an honest acknowledgement of the horror and the folly of war.
With the exception of one mention of how the officers "blundered," Tennyson has nothing to say about why these men died, and for what. All he leaves us with is a glorification of the Light Brigade and of war in general.