Without being an expert in the field, and to simplify it both in terms of the nature of the issue I'm talking about and in terms of suggesting there is a single reason for your question: if women don't get the same opportunities as men, it doesn't matter if they're a bit better or 10x as good, they still won't be part of the achievements.

Inventions of humanity: for much of history in many societies women wouldn't even be considered in consideration for working together with men.

Start-ups, etc.: In the 21st century we have a lot more gender equality, so that many (most?) of the men in the world wouldn't be shocked to work with a woman and consider them equals, but we still have a lot of subtle sexism; the glass ceiling hasn't disappeared.

Here's a good example with some recent data from 538 about gender inequality in movie directing: http://fivethirtyeight.com/datalab/directing-is-even-more-of...