Generally people who hold this viewpoint tend to think philosophy is people sitting around trying to prove whether a chair exists or not.
Philosophical subjects are of great importance to any civilization. What is justice? That is a philosophical question. More specifically, is the Patriot Act a worthwhile exchange of some of your freedoms for some security? To consider these questions is to delve into philosophy, and I'd hardly consider that a worthless exercise.
I wouldn't necessarily say that philosophy is "worthless," but I do think its relative "worth" is overestimated. I will stipulate that it is a method for the pursuit of truth, but its truth is in a category that is different from religious or scientific truth.
It goes like this: truth can be absolute, objective, and connect with reality, but it is only capable of achieving at most
two of those qualities simultaneously.
For example, truth can be absolute and objective, but then it does not connect with reality. This is mathematical/logical truth.
Truth can be objective and connect with reality, but then it cannot be absolute. This is scientific truth.
Finally, truth can be absolute and connect with reality, but then it cannot be objective. This is religious truth.
Philosophy, in the most rigorous sense, is mathematical/logical truth. It is simply the study of how words fit together -- words which were made up by us in the first place. We can agree on definitions and then look to see the implications of the definitions we've accepted, but this has nothing at all to do with reality.