Yeah, that would suck
But, more seriously...
While I think FS2's engine, especially when SCP-upgraded, is pretty stinking awesome - I've never been all that fond of FS2. Remember, not everyone here started in FS2, and that the people doing total conversions, obviously, like the world that they're creating in.
For instance: our mod, Fringespace.
FS2, Allegiance, and Tachyon all came out within a very short timespan. I own all three, have played all three. I liked Tachyon's flight model much better than the other two. That doesn't mean I completely dislike FS2 - I'm hosting the retail files for Turey's Installer!
However, I'm doing a TC for a game that is my favorite, of all time. While I do appreciate that you enjoy FS2 - I'm not going to force anyone to download it to play my TC - although I will refer them, if they want to play another space sim as well. There's going to be a good half-dozen complete games here, with all of the Total Conversion projects, in a relatively short span of time. Looking at the recent first-person space simulator market, that's pretty darn good.
Liek I said - I do understand your point - but once something is moddable, it's no longer about the original. It's about turning it into as many different things as possible from that original base. Of course, there's going to be improvements to the original - but that is only one of the myriad projects in the works now.