I have yet to be told why it is important for there to be as many women in STEM as men apart from statements that I'm sexist for not knowing
The answer is a quick Google search away, diversity increases innovation: https://www.google.com/search?q=diversity+increases+innovati... If you don't agree with that, I'd love to hear why, and why the related studies are false. Can start with this one, which is the first result: http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.685... There's quite the bibliography to pour through there, though, if you really…
We can be pretty confident that if 50% of the population are women then 50% of the best candidates for a given job, by natural aptitude, are women. The same logic applies to minorities as well, so we can be confident that any process calibrated to finding the best person for the job is going to turn up a diverse workforce.
However, once policies designed to enforce diversity come in to play, that correlation will be broken and you just have a sexist/racist/whatever hiring system.