I used to wonder that too, "Why doesn't she just leave?"
Then I became involved in a relationship that eventually became abusive in my early 20's. The changes are subtle at first...and by the time it's really bad, you don't even know how you got there. And if my experience was like most, the reason they don't "just leave" is because the psychological abuse is so much worse than the physical. They isolate you from family and friends, they demean you, they screw with your mind to the point where you really start to think it's your fault.
Mine was such a good actor, that when I finally left (8 days before our wedding) my friends and family were stunned that this had been going on . The day I left, he told me he was going to hang himself. I offered to tie the knot good and tight for him. Lol. He didn't of course, and I won't lie, he had me so screwed up that there was a point that I nearly did go back with him,but by the grace of God, I didn't.
Looking back now, I'm disgusted that it happened, that I allowed it to happen and I'm supposed to be an intelligent person--things like that don't happen to women like me, right? Well it's in every class, every race and may be your next door neighbors--and like I said, it happens slowly. If you know someone that you suspect is being abused, don't ever stop trying to find the truth and don't ever stop trying to help.
Sorry, didn't mean to derail the thread.