Because a large subset of people who don't understand things are unaware of their misunderstanding?
Several people have tried to explain Lesswrongian metaethics to me, only to give up in confusion. Being able to explain something is the acid test of understanding it.
There seems to be a widespread impression that the metaethics sequence was not very successful as an explanation of Eliezer Yudkowsky's views. It even says so on the wiki. And frankly, I'm puzzled by this... hence the "apparently" in this post's title. When I read the metaethics sequence, it seemed to make perfect sense to me. I can think of a couple things that may have made me different from the average OB/LW reader in this regard: