Why still no official full feature FB app in windows store?

It's been quite a while now since the windows store has been opened, so I'm wondering why fb does not seem interested in releasing a win8/rt app. A really good, usable full feature app with notifications via live tile, start screen and toast notification would draw the user's attention to fb activities all the time, which should be FB's goal. Of course, the browser version is there, but it does not draw the users attention the way an app would. And existing apps simply are not good enough. What do you guys think? Is the windows store ecosystem not relevant enough to fb? Is there ever going to be an official app? Is it going to be any good (better than the wp app?)