It's more than that. From a structural standpoint, colonies are extremely fragile. Imagine there being only about fifty meters of material -- concrete, grass, soil, steel, silicon, and so forth -- separating your feet from the vacuum of space. And that's with an old-fashioned cylindrical design. Newer models are even more delicate, since they're made to hold more while using the same amount of material. Considering weapons are designed to cut or punch through metal hulls...

[He trails off, appearing to lose himself in thought.]

...Forgive me. I was involved in an incident where a colony was destroyed. It's an experience I don't like remembering.