Evolution explains not only where we come from, but why we are; why we socialise, why we love, how we form our understanding human morality. It's why it continues to be feared by people who are superstitious.
It doesn't. Here's why:
1) When you use 'why' you're IMHO indulging in some serious conceptual confusion. There's a difference between explaining how something came to be (its efficient cause, if you will) and what its ultimate goal or final value is (its 'teleological' cause). The Evolution Theory deals with the first problem, it's largely useless to answer the second, unless we assume that the world is completely free of any meaning and value and that there is nothing beyond facts that are immediately present to hand.
2) The Evolution Theory is pretty useless in explaining even the genesis of the core of being-human, that is to say: conciousness. The problem of conciousness is one that , again IMHO, wrecks all overtly simplistic forms of scientism.