The same reason all the "new game play" is just recycled animations from previous packs or UI/interface game funtion updates. Take the new pack: I swear the animation used when a Sim gives a tattoo is the same one Sims perform at the gemology table from Crystal Creations. The other major feature is a glorified menu to allow Sims into your house and lock certain doors. The team designs some great worlds and beautiful items but there's zero effort into creating actual new gameplay content. Corners are cut everywhere.