... well. I will be honest, it never made sense to me that wrecks were so easily visible. It's... not so easy to do so fast. Same is true for small moons and asteroids.
But aside from that, for the very same reason mineral packets HAVE to be visible. They are not ships so it stands to reason that they should be as easy to detect as asteroids. I very much dislike exceptions to rules, and so by the "rules" of the technobabble, they HAVE to be visible. That it helps performance is just a plus. And if that reveals colonies, so be it.
That said, I also dislike mass drivers in general, but I understand the "gameplay" need for them, to a degree. I try to never use them when I can, honestly.