When you look at the average citizen's life on this planet, what are the real "advantages" of even unmanned space flight? Do we really want to go there?

A lot--not all, but a lot--of science and exploration over human history has been done basically for the "because it's there" reason. If "real-world" advantages showed up, it was often long after the fact.

For now, that's good enough for me with manned space exploration, but if you want to get into only science reasons, go back and look at our manned lunar landings. Look at what was done, the conversations, the examinations of the environment. No rover could ever match what an astronaut can do on the surface of another world in a single afternoon.

When launch and transportation costs come down--and they will--this will be less of an issue.