Ignoring, for the moment, the fact that philosophy was never limited to the subject(s) of scientific inquiry, I would like to point out that even within the context of science, philosophy has its place. The scientific method itself is a philosophical construct, and contemporary science is by no means beyond philosophical critique; for example, the distinction between realism and instrumentalism - that is, the query of whether scientific theories are true representations of the world, or approximate guidelines and abstracted models with practical use (essentially, do atoms exist as real objects, or are they merely elements of a model meant to explain certain empirical observations?) - and the controversy of reductionism - the idea that the inquiries of every field of academic research can be (theoretically, if not practically) broken down and explained on a scientific base (as Mr Khan, and perhaps even the OP, seem to think) - are discussed as part of the philosophy of science.
And, as I and others have mentioned, the philosophy of science is merely one subset of the field of philosophy proper. Other prominent subsets include the philosophy of mind, language, epistemology, ontology, logic, ethics, politics, aesthetics, and so on.
