...of all this history stuff anyway? It's a question worth asking, even if I'm not necessarily inclined to think that human behaviour has to be obviously practical to be valid. It's more a question of understanding what sort of thing historical research/writing/reading actually is.
Traditional answers to this tend to be of the 'You need to know about the past to know who you are/avoid its mistakes' variety. There may be some truth to this perhaps, but they tend to be points that remain largely unexamined. They're what people have been taught to think about history as a discipline rather than something that comes from an understanding of it.
My approach to the practice of history, and one that I've only settled on in the last couple of years, is that it is essentially a branch of storytelling. Factual storytelling, perhaps, but storytelling nontheless. It weaves isolated (and rather meaningless on their own) facts into coherent wholes whose meanings are created by the historian within a plausible set of perameters. It then presents them as an account of things happening over time. A story, in other words. Or at least, that's my approach for the moment. I'm sure someone will disagree.
But, working from this position, it becomes a lot easier to see the sorts of things that history is for. After all, what are stories for in general? Entertainment, teaching moral or other lessons, helping to construct or reinforce an identity, more entertainment, making a point about the way we think about things, and so on.
The interesting thing is that generally no-one seems to question the usefulness of stories. Compare that to the 'history is a waste of time' brigade and the contrast is obvious. Does a story cease to fulfil its useful functions just because it A: happens to be about the past and B: happens to fit within a range of possibilities presented by surviving evidence? Of course not. It just makes it remarkably awkward to research.