Because the first one came out in 2008. And it's becoming increasingly popular from the iOS port, as well as KH:3D. Plus, they gave us the hint at the end of the iOS port about a sequel, and no info has been given since, just more hints. It's essential to the people who loved the first game to get another one. And if Square Enix has a brain, they should realize another TWEWY would sell quite well.
And because it's my favorite game. Thus making important to me.