I agree with what you're saying to a large extent, but I also think that at present we're looking at it from current adults who for the most part have grown up in a world where these are male dominated fields. If you could hypothetically remove that, then I think the figures would look a lot different. We're all socially engineered and the social engineering around that is natural and goes back hundreds of years. However I think that for roles where the physical side of the role isn't so much of an issue anymore, if the roles were less male dominated then you'd see more women choosing to go into the fields if they grew up with a truly clear and open mind on it.
So I don't think there'd be a massive uptake in women wanting to be labourers, but I can't see a reason why other male dominated fields like engineering, IT etc wouldn't attract more women in that scenario.