What causes these things I'm not too sure. I would guess that pre-marital sex is the primary culprit. Sex stirs up the emotions to such a degree that I think people's visions are clouded to such a degree that they don't think about whether they could actually live with a person day in, day out before getting married. The sexual activity takes priority over the development of communication, which is the crucial key to any successful marriage, and thus when people get into disagreements in their marriage, they are incapable of properly expressing themselves in order to resolve the situation. Resentment builds, and then one of the 3 A's occurs.
Just my theory.