> there are plenty of exciting, risky, and challenging things to do right here on the ground that are likely to have higher priority than manned space exploration for most people for a long, long time.

There will be human ground-level problems (poverty, mental illness, education, etc) to solve right up until the point where the Earth is no more (or is at least non-human-habitable). The Earth is temporary. Becoming less dependent on it as a species is going to be a very, very long process. We can't wait until we solve every human problem* to start.

* Spoiler alert: We will never solve every human problem. Ever.