I conceptualize the history of philosophy as, in part, the source of interesting empirical data about the psychology of philosophy. Nietzsche and Dewey also conceptualized the history of philosophy this way, but I don't think many other philosophers do. There's a lot of untapped potential.
Here are some ways I've put the history of philosophy to empirical use:
* As evidence that it is impossible to construct a detailed, thoroughly commonsense metaphysics of mind-body dualism.I can't resist also mentioning Shaun Nichols's observation of the suspicious lack of historical occupants of one theoretically available position regarding free will.
* As evidence for a relationship between culturally available metaphors for visual experience and views of the nature of visual experience.
* As evidence for a relationship between culturally available metaphors for dream experience and views of the nature of dream experience.
* As evidence that philosophical expertise doesn't diminish the likelihood of being swept up in noxious political ideologies.
* As evidence of the diversity of philosophical opinions that can be held by presumably reasonable people (especially on the character of conscious experience and the metaphysics of mind).
These analyses are mostly not quantitative, but that doesn't make them less empirical. In all cases, the fact that some philosophers claimed X (or X1... Xn) or did Y is treated as empirical evidence for some different hypothesis Z about the psychology of philosophy.
Maybe empirically oriented philosophers typically don't regard themselves as expert enough in history of philosophy to write about it. But I think we hobble ourselves if we allow ourselves to be intimidated. The standard of expertise for writing about Descartes or Kant in the context of a larger project -- a project that isn't just Descartes or Kant interpretation -- shouldn't be world leadership in Descartes or Kant interpretation. It should be the same standard of expertise as in writing about a contemporary colleague with a large body of influential work, like Dennett or Fodor.