Women by default aren't direct communicators. They're non-confrontational. And for them to be confrontational gets them all skeeved out and uncomfortable where they tend to skirt around the issue and avoid confronting what's bothering them.
This is yet another way women are "mysterious" and unreadable. And I have total sympathy for men because men ARE direct communicators and they tend to say exactly what's on their mind and they mean it.
With women you often have to coax it out of them and/or confront them directly in order to get down to the issue and figure out what's bothering them.