The lack of human space exploration really doesn't help in terms of capturing the public's fickle imagination. Sending robots is just not as exciting, even to me. Additionally, NASA's failure to continue to show progress after the huge, dramatic victory of the moon missions was very bad, from a PR perspective. Many people feel that space is over, and that that chapter in humanity's history is closed. Which is very sad, because I think the moon missions were one of the best things we've ever done, as a species.