Yeah, if only we knew how to get it back to Earth cheaply and fuse it with itself we might have another 500 years of fossil fuels delivered by destroying the surface of the Moon.

The future economy in space is so much larger than the future economy on Earth, that it doesn't make much sense to ship non-rare materials back to the surface.

There are some where I think it will, for the foreseeable future, just because they're so rare in the Earth's crust and so plentiful in asteroids, but long-term, microgravity assembly plants are how things will go.