There's a rabbit hole to be gone down here, and I'm not sure everyone will agree on the results - the concession to reality is purely for entertainment, the problem is that once you stop asteroid noises, you have to take out the vast majority of other noises. The only things you'd hear would be the creaking sounds and engine noises of your own craft. No guns/lasers of other ships, no explosions, no engine noises from other craft...
I know what you mean in terms of reality, there would be no sound, but for the sake of gameplay it's one of the things FD have "fudged" for want of a better word. The upshot is that the sounds for everything are truly awesome. Without a doubt the best sound system in any game I've ever played.