The issue is what we explained many times already:
The scenery is NOT developed on FS9. It's developed entirely in FSX. The FS9 version is just the same as the FSX version, except for things that FS9 doesn't support, like road traffic, animated jetways, animated service vehicles, etc.
Since the FSX default scenery is much better than FS9 and it doesn't require buying another addon, we don't design anything outside the airport, because what's outside the airport in FSX is quite enough to have a realistic rendition. The 3d highway obviously matches the FSX default scenery perfectly.
So, the scenery is just like that, because we don't ADD anything to the FS9 version of the scenery something that would be needed only to supply to an FS9 shortcoming.
Much so in this case, were most of FS9 users usually say they still use FS9 because of the large number of addons the have and because often you read comments that FS9, fully stuffed with terrain addons, looks almost as good as FSX, so we just assume that not many are still using FS9 with default scenery only.