I've previously defended purely theoretical inquiry, but it's also worth noting that philosophical assumptions abound in ordinary folk and their ways of thinking about the world. Moreover, many of these assumptions are patently false -- the result of lazy conflation, perhaps, or simply not noticing an (obviously true once you see it) alternative possibility. So I think philosophy is especially good at helping us to notice and correct these common errors in our thinking. (It's no coincidence that my dozen Examples of Solved Philosophy are mostly of this sort.)
(I got thinking about this because of Nancy Pelosi's skepticism about whether life begins at conception -- as if the abortion debate turned on some question of biology. Similar idiocy and irrelevance is seen in debates about whether homosexuality is 'innate'. These people just have no idea about what sorts of considerations are morally relevant. The common conflation of rationality and self-interest is another standard example of philosophical error. A less obvious, but perhaps more important, example is the ubiquitous assumption that property is natural, or that the poor just lack resources, not negative freedom -- mistakes tied together by the failure to appreciate that our institution of property is inherently coercive. I've focused on my own fields of moral and political philosophy here, but there are common, demonstrable errors in other subfields too, e.g. scientism in epistemology.)
I don't mean to suggest that correcting commonplace confusions is the only thing philosophy is good for, of course. But I think it is certainly something philosophers are very good at, and it is sufficiently important to give pause to those who would brashly dismiss our discipline. There's an awful lot of ill-informed public debate that could make much better progress with a little more philosophical input.