Gnomes have never been a popular PC race. I've seen more Tieflings or Drow than Gnomes or half-orcs. I've played D&D for over 20yrs and Gnomes are by far the rarest PC race played. Since Tieflings became available in 2e they've seen a larger following and I'm OK with that (never played one myself though).
There is something that your OP is missing: Gnomes are not exclusively monsters. Adding Warforged (Eberron), Drow (everyone), or Minotaurs (Dragonlance) allows players to choose from a campaign specific list while providing less support to the less popular races. Page space is a limited resource. When the editors are faced with cutting material (as all editors are) they cut the material that is least likely to be used.
Gnome rage exists only because it provides more ammunition to H4ters. Few people play them but everyone complains. I'm running a 4e campaign now and people said, "so they got rid of gnomes eh?" Nope. Open up the MM and they're in the back, you can play one if you like. "Naw, I'll play a half-elf instead." What about you? "Human." Hmm...
I'm not so sure about the whole ammunition for "H4aters". I'm more or less disinterested in the whole edition war bit, so that doesn't affect my feelings or vote on the issue. I've seen in 30+ years of gaming more than a few half-orcs and gnomes. As more optional races have become availiable, I've seen people dabble with them, but not to the levels I've seen/heard about on boards such as these.
I imagine that everyone has their own list of likes and dislikes. For every person that dislikes a race or class, there is another who enjoys it. Just seems that there is room for everyone to have their idea of fun instead of this argument that seems to go on with each included/removed race, class, etc.