Because the picture we have of this woman is that she is a workaholic coldly calculating lone wolf gold digger, except the gold she wants is not wealth but power. It is difficult to trust such a person. If she had a secret lesbian life she would make sense, now she looks unattached to anything but career progression.
What is so very odd is that Obama said that he did not want a social freak, he wanted a person with the commoners touch. Kagen knows how to schmooze with the best of them, but she is certainly not common.