I am incredibly excited about such missions and love reading/following them but really, why "should" we explore space?

Edit: Let me clarify why I ask this, I had once seen some documentary where a marine biologist makes a point something to the effect of - we understand less about our deep oceans than space, but there is a huge delta in our research spending on each. So, why are certain fields more important for research than others, in short, why space?