iWish iCould figure that out too. a variety of answers that iCan think of off the top of my head are:
1) as a feeder, many people join and play the game for a short while, and do not join the forum. then their nation disappears after a few weeks. These people are not interested in regional politics, and NS is just a short interest. They only play with the daily issue, and do not interact on the RMB and other players, let alone the forum.
1a) The opposite of this would be players with a lack of time, or lack of interest, or burnt out (too involved with the gov't) so they don't go onto the forum any more.
2) Other nations can be puppets of other players (invader/defender) that are meant to be hidden, so they will not interact with the regional gov't.
3) and of there is the attitude of what good is the UN if we keep getting repeals so quickly. (there's your lack of caring idea)
4) im sure there are other factors that I haven't though of.
As i mentioned earlier, this
link (in canada) will connect you with a discussion on the future of NS, in how to revitalive the pacifics (in general), invading/defending and other ways of changing the game. however, it seems to have stalled after the jolt forum crashes over the last two-three weeks.