As a parent I would have to say that all of the research on the influence of nature vs nurture is interesting. I want to shape my children to be the best people they can be, but I have to understand that there are lots of things in their personalities that are there from birth and I can do little to change that -- all I can do is provide them with the strategies to maximize their strengths and cope with their inherent weaknesses. For all of us, learning to recognize the difference between who we are by nature and who we are as influenced by our environment in key to a successful life.
Social sciences are important because they help us explain human nature. While I cannot point to any specific piece of research, I do know that over time when I have been confused by something the studies have helped me make sense of it. It doesn't always solve the problem, but it helps.
Social science matters because it can (or can hope to) help us understand how our society should best be set up. It can help us understand things like what sorts of steps need to be taken to prevent things like the recent riots in England. Sadly, social science matters less than it might because the answers it gives are subjective and hard to prove.