> It would be helpful to understand how the culture came to accept women as lawyers and doctors, but why would that be necessary to identify cultural factors as a reason for the imbalance in CS?

It is necessary because the question "What cultural factors cause the imbalance in CS?" presupposes that cultural factors caused the imbalance. The whole point of bringing up that more gender equal countries have larger differences in ratios is to highlight a strong piece of evidence that this is not the case.