Well, I haven't been here that long (uh, only joined in August) and I joined Goblin BECAUSE it was a lower pop server.
1. Because my friends all placed here maybe a month before me
2. I like joining lower pop servers (to help increase the pop and for that more small town feel)
3. I hate overly elitist players (which I've still run into plenty here on goblin, but I can only imagine servers like Gilgamesh).

Though, I will say, because of the lack of pop, it also means that there aren't as many doing the high level stuff.... which means more than likely, those who are doing it are picky because they don't have that much to choose from and don't want to do it multiple times. Kinda works backwards though as you push those wanting to learn away and thus, keeping your numbers low. Players with no patience are the biggest detriments to the server imo. Half my FC won't even play certain dungeons because of players that will simply bulldoze through without explaining anything. One of my FC's healers said her party literally left her behind on Castrum Meridianum (and left half the mobs alive while running through) and she had to just wait for them to finish it without her because she couldn't solo through the mobs. Obviously, not a good experience. But I've also met some very nice players as well who will explain boss fights in detail as well (and I try to do the same when I repeat stuff).