It probably depends on the individual. I mean you have psychotic people that have no empathy for anyone. For them, no one else matters and they can do what makes them happy. On the other end, you have people that may have grown up in that way of life and do not know better. Or may know but don't know how to stop. Those people could stop the abuse with anger management and therapy. In the middle, i think it is a mix of personality and habit. And when all is said and done, it is a form of control. It makes the person feel they are better, smarter, worth more, etc.
But it takes a lot to change the behavior, so if you are in a bad relationship, please do not stay in an unsafe environment. If he/she wants counseling, you can go, but do it from a safe place and they can earn the right to come back to your life on different levels.