I think focusing on "current tech culture" is likely to misdiagnose the problem. There are way more women in investment banking than tech, and I really struggle to believe that Wall Street has a better culture than Silicon Valley, at least a long the lines typically being emphasised, including misogyny, micro-aggressions and mansplaining. If the prevalence of these phenomenon are repulsive to women to the extent that they will forego even educating themselves in a field, much less join top companies in it (the underrepresentation of women in tech go all the way back to high school, it doesn't start at the hiring processes, biased or not, of tech firms), we would expect to see many fewer women in Wall Street. Instead we see many more.
I dunno I hate banks but when I worked for one I worked for a black woman who worked under a black gay man who worked under another woman and at that level she had 9 call centers under her and gave birth on a conference call. This really isn't their weak point.
(Also, the relevant number for Google is 20% of tech employees. They have 48/52 balance in non-tech. The BI link similarly provides business area breakdowns.)
