Space exploration is a search for knowledge and potential resources that should be publicly funded to a certain extent based on budgetary considerations. If we cut all expenditures to the bare bones, funding only those items that are "essential," our culture will be lacking in many areas. If we let other countries explore space while we wait for a budget filled with plenty for discretionary spending, we risk being left behind for centuries to come.
Publicly funding space exploration as well as privately funding it would only serve to advance the rate in which we would be able to explore space. Understanding the great unknown is exciting and the knowledge that is to be gained can't be ignored or overlooked. All possible funding sources should be utilized in order to further our understanding of things this great. Simply relying on private funding would slow our ability to explore space significantly.