Two reasons: 1) Women make less than men often because of career choices. If they make that choice because of shitty behavior in well-paying industries, then we have an injustice on our hands. 2) Underrepresentation of any group puts them at real risk of policies being made against their interests. Imagine a men’s family rights law office staffed only by women. I wouldn’t trust that for best representation. Also see the CA board rules about female representation just announced.
I didn't down-vote you, but a few refutations: (1) shitty well-paying jobs are a fact of life, men often have to (and do) deal with that (e.g. oil rigs, finance, doctors, soldiers). STEM isn't even that well paid (compared to medicine or law) (being a soldier is shitty pay also AFAIK). If you're bent on solving this problem for women only, that's pretty sexist; or is this just the specific instance of this problem where you see most potential upside (unlikely IMO). (2) We're talking about jobs, not policy here. Also, the market adapts - you would just use a different product, a different law office! Are you worried about our tech being "too Asian" because of their over-representation?
