Sometimes it is! When you are discussing a portion of a whole, you can use "a few" in many cases, but not all. When you are speaking using a negative, you often will need "any." For example, if your friend suggests going to a restaurant, you might answer, "I don't have any money" (meaning at the moment). If you say, "I don't have money," it implies that you never have money. You can work hard to re-phrase a question, statement or answer to avoid "some" or "any," but why do all that work?