Widespread and institutionalized sexism. Poor treatment of mothers and expectant mothers, as well as women in general. This is a company that would rather have a free smoothie bar and a PC cafe where people can slack off during work hours than a daycare center. On a campus of over 1000 people, there is literally one small closet for women to pump breast milk in.
A friend of mine told me recently that HR set up a meeting with her specifically to tell her that because she didn't have a note specifying a medical restriction from her doctor during her pregnancy, that if her performance dropped, she could be fired and would have no legal recourse. This person is clearly very productive and well regarded those she works with. She said it added to her already high level of anxiety about her pregnancy.
In addition to that, all you have to do is look at the ratio of women in leadership positions to realize that there is institutionalized bias against promoting women. This doesn't seem to be improving with time, despite all the lip service management pays toward an effort to have greater diversity in leadership.