1) There are multiple fields available for new entrants to the labor force to pick from.
2) Some of these have better working conditions than others.
3) Women tend to be a bit more mature than men at the age at which one picks a career and are more likely to consider working conditions when doing so.
This has nothing to do with whether people are caring that someone is screwing someone else or not per se. What it does mean is that improving working conditions in some fields would likely draw more women in, if the above theory is correct. I have no opinion on the theory itself.