People striving to survive every day, dying of famine & health, something that would be easy to solve if we put our mind to it. Why pollute the environment for research that might not help with space exploration what-so-ever? We could use that money to educate people who suffer of poverty.
It really not the space exploration it self that is using most of the money, rather the skilled workers needed to build the space craft. It is also part of human nature to explore the unknown. There are many examples of this including the time during the middle ages. When Galileo tried to explore because he was a free-thinker. It would also help us answer some of humanities questions. Like how did the universe was created?