Manual vs. Game
I always found the manual of the original Homeworld to be very strange. It describes the various civilizations on Kharak in quite a lot of detail, with many personal stories of Kiith and so forth. It really fires the reader's imagination for this place. From reading the manual, you might even guess that there could be civil wars within the fleet or just general politicking on your path to Hiigara.
And yet... 3 missions in, all of it becomes completely irrelevant. Kharak is burned, and any notions of Kiith, politics, and so forth are completely lost. So what was the point of spending dozens of pages in the manual on this?
So that you would know that something was lost. A loss only matters if what is lost was actually valued. In order for you to value Kharak's civilization, you needed to know it. You needed to be invested in it. And that's the point.