Despite my long explanation, I think the answer/reason is quite simple.
In Australia, Govt policy allowing women to work after marriage was developed in the late 1960’s. However, the policy was not implemented until 1972. Also, the policy did not include married pregnant women and it was some years before the Australian Govt allowed married pregnant women to continue working. Even in the 1980s, I recall adults complaining about women taking jobs from the men.
Case & Point:
It has only been 45 years since Govt policy in Australia allowed married women the right to work. Even then, and for many years after, there were significant restrictions on women being allowed in the workplace, as it was viewed as a priviledge. To use an analogy, gender dominance in the workplace based on academic discipline, is not dissimilar to Australian Aboriginal Health, who after ~240 years, are still building up their amunity to disease introduced to them by their caucasian counterparts. For women in the workplace, the real shift started in the mid 1990’s, after introduction of Govt policies such as EEO & anti discrimination. Not because of the policies alone, but the distance we had progressed collectively in such a short period of time. In reality, women have only had workplace flexibility for the last 20 years. Despite recent years showing real changes in the statistics around women in male dominated industries, this is only the beginning. Until women like me, who remember the workplace restrictions once placed on women, are retired or long gone, gender balance is always going to be evident, even in a subtle way. We may not agree with the reasoning, but there are still many women out there who believe it is the role of a man to provide. Like the Aboriginals, we have to breed out the old ways, which simply takes time.