Well, it's lore not an in-depth story. Lore is small fragments that require interpretation a la dark souls whereas most media is presented in a cohesive and easily digestible narrative. This lore probably took bungie much longer to craft than the story of many other games and is far richer, but it requires user engagement. It is not a passive medium but it is unique because we take ownership of the story through our theories (not me as an individual, but the whole destiny player base)