I started reading OB because I liked Robin Hanson as an economist. I continued reading because I liked Yudkowsky as a writer. I agree I'm still part of an unrepresentative sample (people who are willing to read and consider Yudkowsky's long ramblings), but not everyone found the site because of an interest in rationality per se.

Unfortunately, anyone taking a college course probably would be interested in rationality qua rationality. But the lessons are still valuable for those poor souls who, like I once was, are still religious despite it. The same for those who are religious fence-sitters.