It's quite possible to imagine that direct or indirect sexism leads to a low percentage of female Go players.

At the 2010 EGC there was a list of amusing reasons for losing published on the main bulletin board, gems such as "Too big boobs" came up. Some might consider that offputting. You might argue tournament photographers tend to focus on women. Or that men tend to treat female players differently from male colleagues. Hard to document this type of thing. Anyway - it's a possible line of argument.

My own view would be that strategy games are generally regarded as a male activity, and the social conformity tends to exclude women from the game in the first place, this added to the predominently male environment, which one can argue as inherently intimidating. (Pair Go is supposed to create a neutral environment.)