There are alot of variables why people frankly don't play anymore.
Some of the biggest ones are:
1. Freelancer is an old game and people are having a harder time acquiring it (legally) due to a lack of production.
2. Many feel that Discovery/Freelancer is becomming Noob-Unfriendly and feel as if it's a waste of time.
3. Some cite that a lack of Dev-Factional Cooporation makes the game unplayable and too tightly controlled by the Developers, making people lose faith that they can change anything in the mod for good or worse and just leave.
4. Real Life, this is a big one, years ago alot of people here were in College or Highschool, now the troubles of life are catching up and they have to spend less and less time on the computer and more in the real world dealing with stuff like bills and other important items.
5. People also feel that the game has become 'stale' and boring, that nothing interesting can come of this mod now and that it's time to move on to another game/mod.
Those are some of the reasons I've gotten. *shrug* All in all, yes people are leaving slowly, but it's simply a part of life itself, we can either adapt or do nothing and wither away.