Why do all of the Maple copy cat games keep dying?

I've been wondering the same question a long time.

I said this in another thread but I wish a company which has the tools and the experience on making sidescroller platformers like Capcom or Sega would decide on making a fantasy 2d MMORPG. I mean, look at megaman ZX advent, the game is almost 7 years old and it still looks better than maplestory at the same time its gameplay is awesome.