The physical and emotional damage caused by family violence is massive. Some people see spanking a child as a form of abuse because it can cause a tremendous amount of emotional trauma. I recently read a journal article that had some astonishing results regarding family violence. They found that physical aggression was highly prevalent in families who had young children. Only 30% of the families reported at least one type of severe aggression; 59% of the children had experienced aggression from both parents. They also found that parents were more likely to engage in physical aggression towards their children than their partner; however, parents use more severe acts of aggression against partners than children. Women were more aggressive to their partner and children than men were. The extent of partner aggression stemmed from previous aggression on them from their partner. Younger parents are expected to have higher levels of aggression present in their families because of the lack of parental experience.
There are several motivators why abuse takes place in a home. Parents are abusive for several reasons. Stress, frustration, anxiety, cruelty, power struggle, accidentally... and it also depends on the type of abuse. Lots of parents have children way too young, and don't know how to take care of themselves, let alone a child. Some parents are on drugs which alters their mental state... or they abuse alcohol. Occasionally you will even see a parent who doesn't seem to have any natural affection for his or her child. None of this to say that child abuse is excusable. It is not. But in general, those are some of the reasons behind it. When you grow up in an environment that is unstable and emotionally or physically abusive, it is hard to stop the cycle.