It's science. A lot of science is measuring and documenting the completely obvious - because there's a lot of interesting and not-obvious stuff hidden in the obvious.

If this is so obvious, how do people get away with blaming "the pipeline" for their own tendency not to invest in female entrepreneurs?

Because no one on Hacker News has ever questioned whether sexism exists in the startup world.

It's funny to think that in 30 years, there will be a TV show called Mad Geeks ... recounting the tales of the good ol' boys of Silicon Valley. Their sexist ways will be so funny to watch (exaggerated of course ;-)