Maybe because we don't agree with those complaints? Personally I don't think HW's zones are very big, they are about standard for an MMO, from the ones I have played. They are certainly empty, but that is either due to PS3 constraints or developer problems. The idea of huge, densely populated zones is a good one, and one we should be asking for. For crying out loud, we still have zone transitions, instead of being able to move from one zone to another seamlessly (without a loading screen) like pretty much every other MMO out there.
And saying that the PS3 is holding nothing back is patently false. Even the devs have said that the current zones are already pushing what the PS3 can do, and they aren't that big. Why so empty? Maybe because the PS3 can't handle it all. The PS3 has limited the UI, it's barely changed, barely any of the sorely need features have been added, and devs have stated it's because the PS3 lacks the memory to do anything more. And then lets discuss the graphics. We still don't have proper hardware anti-aliasing. We get blurry low res textures, even though we know for a fact they have higher res assets. We get barely get real physics in the world or on character or mounts, low poly count models for characters and armor. Yeah we have flying, but it's literally running in the air: mounts don't dive, turn or bank realistically because this game doesn't use proper physics. That new reflection effect that came with HW? Barely used, and when it is you can tell it's pixelated and very low quality, and you don't get lighting effects reflected properly either, it's static. We still don't have volumetric fog or similar effects like proper rain and thunder, and whatever they use to create the skybox is low res too. It's especially apparent at night, the "milky way" effect looks like a painted on texture. The list just goes on and on.
Now certainly, some of what I mentioned above hasn't been done due to a mix of developer resources, design decisions and the like. But you cannot, with a straight face, tell me that the PS3 isn't the biggest factor in all of it. It limits practically everything a dev could do with this game.