SL was not mentioned in the original because it was not relevant at the time, besides it is a new concept by S-E, to further points of the series... as time passes people learn grow and obtain knowledge of their surroundings making new discoveries all the time, are you saying that these characters should not evolve and learn more about their world (or rather we learn more about their world conversely), that their science, technology, and understanding should be at a constant flatline in the evolutionary paradigm, do we not now know things that humans did not know 20, 30, 50, even 100 years ago? what you're saying is ludacrise, for if they stay at an evolutionary plateau then the story dies, and that is not what the fans want, no one (normaly no one) want's their favorite story to end and if it does they almost always want another story set in that same world possibly even with the characters they know and love... just because it wasn't explained in the past does not make it irrelavant in the present, if that was the case humanity would have ceased to exist aeons ago...