The moon is the obvious stepping off point for the other planets in the Solar System.
So what does that mean and why ought it to be valid, important?
Besides Mars and various asteroids, it's unlikely that man will be going anywhere else for many centuries.
Venus? Its atmospheric pressure is 90 times Earth's pressure. Its surface temperature is over 800 degrees F.
Jupiter? A gas planet. Jupiter's moons? Almost all of them pass through Jupiter's lethal radiation belt. And, Jupiter's intense gravity deforms the surface of all of its moons, which means that any man-made structures on, or below, those moon surfaces will be degraded by constant geological stress.