If I could answer that, my work would be done.
A lot of it is historical and it's been going on for a long time, but I think a lot of it is war. One of the things you see in times of war is that women are often pushed to the side, “Wait. We're going to fix things. We're going to make peace and then we're going to let you into the process.” That's where the international community has a role and an obligation to say, “No. We're going to make women part of the process. If we're going to have ten people sitting around making a peace decision, we want two of those to be women or this isn't going to move forward.”
Why women are marginalized is a longer question than I think anyone can answer. I think the solutions are about pressure and having the will to back up what you say. “No, I'm not going to give you this until you do these three things.”