Earlier quoted context omitted.
Manuals in the 90s were sometimes actually fun . I still occasionally reminisce about that time in primary school, when one of the classmates bought (well, his parents did, I suppose) an original, boxed copy of StarCraft. He used to briefly lend the CD, and at some point copies of the CD started circulating, and he would just share the CD key with a few people - but in between, he lent me the manual . I think I was t…
I fondly remember the manuals for Homeworld 1 and Homeworld Cataclysm. More than a hundred pages each, the second contains extensive in-universe descriptions of the units, talking about dispenser jamming issues in the minelayer corvettes and the odd center of gravity on the interceptor fighter due to its offset gun. Complete fluff, of course, with zero impact on gameplay. Perfect nerd bait, like those giant books of…
Skimming from the dozens of pages I would love to have read back then, I think this may be the case of writers creating a detailed setting for the game early on - only fraction of it could become part of the gameplay, but presumably designers and writers were using it as a reference. And, come release time, it didn't hurt to include the world-building bits - it might just get some players to enjoy the game more (I know it would've had this effect on me), while the alternative, back then, was for those details to never see the light of day.
And/or maybe they hoped to make some follow-up games, or tie-in novels, etc. - then including those details was both important to solidify the fictional universe, and would drive some secondary sales for the game itself.