[@Sophrus] A belt is not a ring. If you look at some of the asteroid belts in the Solar system (like the ones in Jupiter's orbit, or the Oort belt) they can be jam packed with thousands of asteroids. They are many, many kilometers wide and tall, so establishing a base in the middle DOES serve a purpose. Plus its outta they way, so its always a good fallback position.

Ps: of course you can always take a mile long dreadnought and blow every asteroid to milimeter sized debree, but that would take forever