1) There are diminishing returns on talking about improving rationality.

2) Becoming more rational could make you spend less time online, including on LessWrong. (The time you would have spent in the past writing beautiful and highly upvoted blog articles is now spent making money or doing science.) Note: This argument is not true if building a stronger rationalist community would generate more good than whatever you are doing alone instead. However, there may be a problem with capturing the generated value. (Eliezer indirectly gets paid for having published on LessWrong. But most of the others don't.)