It's because Sims 4 is the newer game of the franchise with newer graffics and is a life simulation game with millions of players that have different play styles one major group being family players. Lots of people that play/played sims 3 now play sims 4 .Sims 3 generations was the standard set for family gameplay by the sims team i dont see why family players should expect less than the standard. It will be a tool to flesh out the life stages and fill the holes in game play that makes all sims feel the same. There are also generational players like myself that have been playing since childhood and want the best for the game for every play style. It is wise to draw from the best features of the past and improve upon them while also blending in fresh new ideas.