A combination of things: All the talk from Aria, plus the fact that there was originally supposed to be a mission on Omega.
Add to it that it's an obvious place to stage a stand-alone DLC package and you can see how people are adding 1+1 and getting 2.
What would be the point of playing it now we know it'll make no difference and be cut off from the rest of the galaxy at the end? Good luck growing crops on an asteroid in hard vaccuum.