I think one of the important factors to remember is like someone else pointed out - just because they leave doesnt mean the abuse stops. It may even esculate. Especially when there are children of the relationship as there is now a legally binding tie to the abuser for the next 18 years. The abuse after leaving may feel worse for their victim simply because they are now aware of the fact that their partner is abusive but they cant stop all of it. Really it can all boil down to a case of the lessor of two evils.