And I can tell you exactly why. Imaginesim is basically locked in, as long as they continue support for FS9, when it comes to new technologies and advancements.
The big difference between ImagineSim, and Fsdreamteam NOW, (other than the fact that they are probably a little more talented) is the fact that they don't develop for FS9. By developing for FS9, they are killing their future, because their sceneries will be the same, and same again, just to make it compatible with the FS9 engine.
I bought KDEN from FSDT back in 2009, when their scenery was quite good for the time (because FSX and FS9 were more equally popular), but you can see, that their quality hasn't changed at all in this time.
FSDT, being the wise developers they are, were smarter than this, and made the decision a few years ago to quit FS9. Look where they are now.