That's a LOT of asteroids, but it's still mostly empty space... ;D
Atoms are mostly empty space with electrons orbiting a center of protons and neutrons. (In theory)
Solar systems are mostly empty spaces with objects orbiting a star or two (or more) at the center.
Galaxies are mostly empty spaces with stars, nebulae and debris orbiting a center of gravity or a massive black hole.
The universe is mostly empty...
Spot the pattern yet?
In a way its disappointing, makes me think there limited supply of the rocks that would be useful for human exploration / development in space.
I keep thinking what Asteroid field was like in such films as Star Wars, that amount of debris would be useful or worthwhile to harvest.
All we need are a few dense metallic asteroids a safe distance from the sun to safely mine and construct with. I have read since I was little that the asteroid belt was nothing like what we see in Star Wars and the like. You can be right next to an asteroid in the main belt and not see another one in any direction, and the exception to that would be extremely rare.