I guess you kind of answered the question I had in mind. Most "western" people seem to see anonymity or even pseudoanonymity as something you use when you have something to hide, something you don't want traced back to you. Everything else, they don't seem to mind having their real name (or a pseudonym that they make little attempt to disguise) attached to. Or, on a different level, people believe that you need to have some kind of identity that you care about, a reputation that you want to uphold, to keep discussion civil and meaningful, and that this should be the key element differentiating an online community.

On the other hand, the default in my mind is anonymous discussion. You only don a pseudonym or reveal your true identity when it's actually relevant to the conversation, and immediately stop when it isn't -- people usually don't care about who I am, but they might care about what I have to say. As an example of this, I've browsed Hacker News daily for over a year now, and just recently got around to creating an account. I still feel uneasy about it, even though I'm posting with nothing but a pseudonym, and not posting about anything that I would particularly care about having traced back to me. I doubt Hacker News would have the same culture if it had allowed anonymous posting, but I certainly would have started contributing much earlier if I didn't have to create a pseudo-identity to do so.

It's important to note that while it might be true that Reddit serves as the West's 2chan, the two deliver markedly different experiences. 2chan being as enormous as it is (millions of posts per day) should indicate to you that there is some itch that a giant collection of anonymous textboards can scratch that Reddit can't.