Having been stuck in an abusive relationship before, it's not always as easy as it seems. I constantly heard "just leave him!" but he controlled literally every aspect of my life. He took over my finances, he chose my clothes, he chose what I ate, who I spoke to etc, etc... I couldn't get away as he made sure that I had absolutely nothing without him. If I tried to rebel then he'd beat me unconscious so that I wouldn't do it again. These kinds of manipulative bastards also make sure that they cut you off from anyone that sees them for what they are. They make sure that they're all that you have left, they destroy you mentally until you start to believe that you deserve it and that they're right for treating you that way. It's extremely hard to escape from that kind of situation. Hell, even if you do get away, it doesn't mean that they'll stop abusing you. My ex stalked me, tried to kidnap me and threatened to kill me, even after I'd managed to escape. Why do you think you hear so many cases where an abusive ex murders someone? These people are dangerous and you learn to placate them by doing whatever they tell you because you're scared shitless of what they'll do to you if you refuse to do as they say.