The point is not just exploration, the point is eventual colonization of space. We eventually need to move beyond the Earth as the only habitat for humans. Arthur C. Clarke said, "The Earth is just too small and rickety a basket for the human race to keep all of its eggs in," Try reading some books about space colonization - "The High Frontier" by Gerard O'Neill is a good one.
Since we are the only intelligent race that we know of, I think we have an obligation to spread, rather than sit here passively until we are snuffed out by the next Chicxclub asteroid, the sun heating up, or some other disaster