I remember seeing a study using PISA data (I think...) that found an interesting difference between boys and girls, which could explain much about career choices.

Boys who scored very high in STEM tended to have that as the only area where they were at the top. In other areas they might be good but usually not outstanding like they were in STEM.

Girls who scored very high in STEM tended were much more likely to have at least one other area in which they also scored very high.

People have a tendency to choose an occupation that fits with something they are good at. If the aforementioned study is correct, we'd expect to see boys who are good at STEM subjects to be more likely to go into a STEM career than girls who are good at STEM subjects, because for the girls it is more likely that they also have a non-STEM subject that they are as good or better in than their STEM subjects.