I agree that it's impolite. It's just that it's become so commonplace that a lot of people don't really think about it.
I tell people I'm a writer. It's true. I write. And when they ask me what I write, I tell them: poetry, fiction, nonfiction, essays, articles. It's funny because I really get grilled sometimes. I think by telling people I have an artistic pursuit I'm actually worse off than telling them I'm on disability. Either is frowned upon in most circles, from what I gather. Both are misconstrued as 'laziness'.