I think there are several reasons for the imbalance, some valid, and some definitely not. Women are generally physically weaker than men, and this feeds into the idea that women can't ring heavy bells. I have seen women turn in Birmingham Cathedral tenor, and the superior skill some women have was also amply demonstrated in a presentation for St Martin's Guild some weeks ago. I speak, in awe, of both as someone who can just about manage a 1-ton bell.
However, MCPism is alive and well. A lot of men assume women can't ring heavy bells, make calls or do other things as well as men can. I suspect ego comes into this - some men can't cope with having their ego dented. The flip side is that some women I've encountered in ringing circles seem to be less ambitious than men (sweeping generalisation; remember all generalisations are false - think about it!). In my limited experience of running practices I've found that many women are not as keen as men to progress in various areas, as well documented in the RW articles.
I suspect the truth lies in both these observations, and probably others too.