I think I'm part of that group for whom this story-telling method doesn't really work, and I say that as a fan of SotS, who owns it twice (once on CD, one on steam when they sold that complete collection), and will be picking up the sequel. Reading the backstory for SotS, and Homeworld, was very interesting. I like the background of the races. But I do not experience it during normal play. Apart from the drives, all races do the same kind of crap, really. Certainly when you're playing them, and the differences in the AI are marginal.
As much fun as I have had playing the game, the only game that I remember narative-wise was the one where we randomly had a small galaxy with 3 players being Liir and the other human. Because the Liir could all speak each other's language, they forged an alliance almost instantly, and when one researched human language, the humans got an invite and the game ended then and there without any player firing a shot. But I don't remember that for it's epic story, I remember that because it was funny. I've always felt disappointed that none of the backstory really ended up in the game, or translated into gameplay mechanics. Yeah, I guess you can make up your own narrative as if you're doing a Let's play. But that does not happen automatically for a lot of players, myself included.
If they make more tools to better immerse myself into the background of the races in the sequel, and those backgrounds have in-game consequences, I might change my mind. But frankly, I'm betting this isn't just a principled decision about storytelling in games. This is a cost-cutting trick. Writing backstory and putting it in text messages is cheaper than making a story driven campaign, and Keberos assumes (probably correctly) that a missing campaign won't be a dealbreaker for most of their customers. Baring other evidence, I'm assuming this philosophy is just as much marketing bable as Blizzard stating that their customers WANT to be online all the time while playing Diablo III, and any convenience this has for them (lower costs for Keberos, DRM for Blizzard) is of course purely coincidental.