It's not supposed to be an alien culture in a far off galaxy. It's supposed to be another version of us, we're supposed to be the 13th colony of Kobol, they're the other 12. It's not a lack of imagination on their part, it's a lack of understanding on yours, the culture is supposed to be largely us, with just enough differences to make it sci-fi. That's one of the basic concepts of both versions of BSG.
Kind of like the lost tribe of Israel?