But that's just the way asteroid belts are, right? As C-3PO will tell you, the chances of successfully navigating an asteroid field are slim to none. It's basically a stampede, only instead of pissed-off cows, you're facing millions of huge murderous space boulders.
Here's a pic of the asteroid belt in our solar system. It kind of looks just like the one from Star Wars:
Although it could really use a couple of extra Dewbacks. We'll take care of that in editing.
And there are loads of asteroids in that belt, true enough -- it features about half a million asteroids that we know of. However, there are also lots and lots of miles for them to cross. Lots and lots. To the point that when NASA had to send a probe through it, their scientists said the odds of colliding with an asteroid were one in a billion. So basically Han could have blindfolded himself and steered through our asteroid belt with his dick, secure in the knowledge that the odds of hitting an asteroid in the middle of an asteroid belt aren't a whole lot higher than the odds of you hitting one while driving your car to the grocery store.
That sounds crazy looking at the picture up there, but no picture of space really conveys the distances. For instance, once upon a time, our asteroid belt had way more asteroids in it (about a thousand times more, in fact). Even if Han had to fly through that density of asteroids, he'd find that each asteroid has a mind-boggling 400,000 square miles to itself.
It's empty. That's why it's called space.