This may be a bit of an ignorant opinion but there are some things that require a human touch and the ability to quickly adapt to a multitude of planned and unplanned situations.
It costs NASA a vast amount of money to maintain a manned presence in space. Many people have called for the scrapping of a manned space program in preference for robotic explorers. In my view, although robotic probes are essential to seek out the nooks and crannies of the Solar System, we mustn't forget that manned exploration is essential for us to develop as a species http://www.astroengine.com/?p=4151