"I'm probably 20 per cent atheist and 80 per cent agnostic," says Pitt. "I don't think anyone really knows. You'll either find out or not when you get there, and then there's no point thinking about it."
Why should you care? No reason, because it's not a matter of should or should not. A person has expressed an opinion: whether you care or not is immaterial to that expression. If a particular person's opinion does not matter to you then take no heed of it.
What I find disturbing about your comment is the dismissivness. An accountant says she is an atheist; is your response, "Why should I care what some accountant thinks about anything other than accounting?" Can no person express an opinion of merit other than as that opinion relates to their occupation? What absolute nonsense!