As much as robot missions would. Observe the terrain, attempt to scout for potential Helium-3 mining locations. That sort of thing. If not that then perhaps for the sake of symbolism - sending a message to the world that humanity now once again has a presence on the Moon and that this time they are there to stay. I of course think that robotics is the safer and more economic option but manned missions will have a deeper impact on the psyche of the country who sends them there (if not the whole world). If it spurs public interest it may end up assisting commercial ventures (whether tourism or later mining) later along the road.