I have some conjectures.

1) People tend to hold beliefs for social reasons. For example, belief in theism allows membership of the theist community, the actual existence of a deity is largely irrelevant.

2) For most people, in order to maintain close social relationships it is necessary to maintain harmonious beliefs with nearby members of your social network. Changing your beliefs may harm your social ties.

3) The larger your social network, the more you have to lose by changing your beliefs.

4) Less Wrong encourages questioning and changing of beliefs.

5) On average, women have larger social networks than men.

6) Less Wrong encourages the adoption of strange and boring beliefs, largely based in maths and science.

7) Advocating strange and boring beliefs does not signal high status, rather it signals a misunderstanding of widely accepted social norms, and therefore poor social skills.

8) Much of a woman's percieved value as a human being is tied to her ability to navigate the social world, men may be forgiven for making the occasional faux pas, women are not. Women are therefore strongly averse to signalling poor social skills.

Some predictions:

1) Willingness to join Less Wrong is inversely proportional to the size of your social network.

2) The exceptions to this rule (Less Wrong members who have large social networks) will be members of fringe groups, where challenges to group beliefs are normal and do not lead to reductions in social status.

3) Less Wrong will never be popular among people with large, mainstream social networks, as long as it advocates self-examination and questioning of recieved beliefs, and promotes discussion of strange and boring beliefs. It will never be popular among women, and the women who do post here are unusual in some way.

ETA: for the sake of complete accuracy, let "fringe belief" be defined as one that is held by <0.1% of the population of the host nation.