Because college is where women are driven out of computer science, by behavior from professors and peers. If you want to talk about fields where men are driven out (and they do exist: primary school teaching and nursing come to mind) go to a thread about those. But either way, derailing this discussion doesn't help.
A lot of people take that for granted based on anecdotes, but actual data is elusive.
Some things we should expect to see if this theory is correct:
* CS student gender ratios close to 50:50 at admission
* A relatively large change in CS student gender ratios between admission and graduation, compared to other majors
* A relatively high rate of "misbehavior" (e.g. sexual harassment) in CS programs and/or the tech industry, compared to other fields
From what I can tell, though, we don't observe any of those.
> If you want to talk about fields where men are driven out (and they do exist: primary school teaching and nursing come to mind)
The same questions could be raised about those: why are we so sure they're being "driven out" at the college level?
Here's a paper investigating the causes of gender imbalance among primary school teachers: https://etd.ohiolink.edu/!etd.send_file?accession=ysu1515846...
The men interviewed for the paper disagreed that discrimination, social barriers, stereotypes, or other forms of injustice play a role. ("I don’t feel that there is any injustice… men who want to teach, are able to. It’s not like we’re being held down.")
It also points out that a greater number of men than women choose to go into primary education during college, which is the opposite of what we'd expect if they were being driven out by professors and peers.