Because the pool of male engineers is ~4-8x larger than female candidates, so hiring 50% women is intentionally hiring worse employees because of their genitals.
The pool is skewed male because of sexist bullshit. Computers used to be viewed as predominantly clerical and thus women were far more prevalent. And it’s patently false to assume it has to effect hiring quality at all.
Nonsense, in countries with higher gender equality women naturally flow to careers more in line with their strengths, tech is not one of them. Men and women are not equal.
The interview process may be the same but the hiring choices ultimately must be discriminatorily skewed to achieve 50% women in the workforce if the percentage of women among the applicants is way less.
I've been part of a number of recruiting exercises to hire 20-100 SWEs at different levels. DE&I is front and center, both implicitly through corporate culture and explicitly through reminders, comments, etc in the process. It very clearly influences outcomes.
I've come to terms with it as the results have been pretty impressive in the last place I worked. It creates a 'put up or shut up' environment where excuses don't really get much traction. I led a team of eight SWE and six were women, representing both the top and bottom of skillset and teamwork in my crew, one in particular being easily top three engineers I've worked with in my 25 year career. She has the potential to go very very far.
Ok, but why is the pool of engineers 80% men when the population is 50% women?
I'll offer one explanation: because the women that go into the field get treated like shit and burn out. There are many documented examples of tech businesses with systemic sexual harassment problems[0]. If your business takes steps to ensure its corporate culture does not fall into that same trap, then women who don't want to be sexually harassed will flock to you. That's how you get 50% women in a sexually-discriminated field: do the hard work of actually rooting out sex pests.