Between Google Play, Amazon App Store and Apple's iTunes App Store there are roughly 1,500,000 million apps. Releasing another one isn't a guarantee of any real exposure. The reality is the only people that would download it are the people already playing the game. I'm not saying having mobile apps wouldn't be nice...but WIS should do it based on improving their service and retention rather than any unrealistic hope that it's going to draw any significant number of new subscribers to the game.