Because the assumption from most people who've quit the original (and those that still play) is that it might be like Maplestory in it's early days. While other people have Warcraft 3, Counter Strike and Quake for me Maplestory was the game that I played as a kid so it has some really good memories attached to it. People wanted Maplestory 2 to be like it's prequel used to be, so Nexon are relying on the fact that people will play it solely for that fact.