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.