I agree that government should not be in the business of space travel except for national defense. However, NASA is not going away any time soon. I hate to see my taxes wasted on experiments in the space station that would barely qualify for a high school science project.
Therefore, if we are going to spend the money, lets do something worthy of the cost and the only thing I see that could capture the imagination of the current generation is a mission to Mars.
Private industry could do it better, but what is the financial incentive for doing so?