The bigger you are, the clearer it becomes if you have gender biases in your hiring, pay or advancement. Walmart is a current example.

eg. http://www.nytimes.com/2010/06/04/business/04lawsuit.html?_r...

They are more likely to be in the public eye. More visibility = more chances of being attacked for being sexist/discriminating = more programs and "support" to hire females, underrepresented minorities etc.

A startup is working hard just to survive. This is a survivorship bias often ignored by media and report likely because its not politically correct.