E
xplanations can come in a variety of forms. It's one thing to explain a phenomenon in general, and quite another to explain a particular occurrence of it.
Take birdsong, for example. It's one thing to ask why birds sing at all -- and answers such as "to maintain territory", "to attract mates", and "to communicate distress" are reasonable enough.
But when a bird opens its mouth to sing in this particular moment, why does it sing? It could be doing one of the activities mentioned above -- but birds sing all day long; are they really so concerned with this small handful of activities?
No; birds may have their powers of the voice in general to perform certain functions; but I am nigh certain that birds enjoy singing. That when they make their distinctive calls, there is a thrum of pleasure that rolls through them, and encourages them to take up song whenever they can. It is like a man going for a walk, or singing, for that matter. The powers develop, perhaps, for very pragmatic reasons; but they take on a life of their own, and begin to exist for their own sake as well.