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Toylines in general are like this. At best, packaging has a blurb about the story and a quick bio giving the rundown on the character. At worst, there's nothing in or on the box explaining the world the characters live in. Some may have a TV or movie tie-in (if they're not based on one in the first place), but other than that when they say it's All There In The Manual, they mean it's All There In The Manual.
For BIONICLE - besides the fact that the toys are some of those have no story material included at all - the main story has to focus on current toy sets, so information on other characters and general world-building can be the domain of supplemental guidebooks and web-published side stories (and occasionally Word of God).