People have difficulty understanding the motives of people who are involved in abuse. Why people choose to abuse other people is a common question. Why (adult) people who are being abused choose to stay in abusive relationships is another. Neither of these questions have easy answers and even the strongest attempt to educate yourself as to why people might make these seemingly irrational choices will not lead to complete understanding. Abuse situations must be lived in and experienced before their internal logic makes any sense. However, we can try to do our best to understand.
Why Do People Abuse?
The first question, "Why do people abuse other people?" has multiple answers. Some abusers learned to abuse from their parents. Their early history consisted of receiving abuse themselves and/or seeing others abused (one parent abusing the other or their sibling, etc.). As a consequence, abuse is the normal condition of life for these people. Such people internalized a particular relationship dynamic, namely the complementary roles of "abuser" and "victim". They are familiar with and fully understand the terror of being the helpless victim from their own childhood experience. The opposite of being a victim is not simply opting out of abuse; it is instead, to be abusive. Given the choice between being the out-of-control victim, or the in-control abuser, some of these people grow up to prefer the role of the abuser. As they become adults, they simply turn this relationship dynamic around and start acting out the "abuser" side of the relationship dynamic they have learned. By choosing to be the aggressor and abuser, they may get their first sense of taking control over their own destiny and not being at the mercy of others. That they hurt others in the process may go unregistered or only occur as a dim part of their awareness.
Abusive behavior can also result from mental health issues or disorders. For example, someone with anger management issues, a diagnosis of intermittent explosive disorder, or a drinking or drug problem may easily get out of control during arguments (e.g., because there is something wrong with their ability to inhibit themselves at the brain level) and verbally or physically strike out at their partners and dependents.
Still other people who abuse end up abusing because they have an empathy deficit, either because of some sort of brain damage, or because they were so abused themselves as children that their innate empathic abilities never developed properly. Such abusers cannot or will not relate to other people as people, choosing instead to treat them as objects. In effect, they confuse people for things. They treat people as though they were there solely for their convenience and do not otherwise have an independent, important life. Abusers who treat people in this manner are very likely psychologically ill, and possibly medically ill as well. They may have an antisocial (sociopathic, psychopathic) or narcissistic personality disorder, and they may have anger or impulse control issues and substance abuse issues on top of that! Such people may abuse because of the benefits they receive from doing so, for instance, sexual or financial gratification, or the simple allure of power over other people's lives. Think of any dictator that springs to mind and you will have the personification of this type of individual (Saddam Hussain seems to fit well and comes to mind easily). The character of Tony Soprano from HBO's television series, "The Sopranos" is also a good example of this type. What makes Tony's character so interesting to watch is that he is aware of his tendency towards narcissistic sociopathy and struggles against it at times with varying rates of success.