In answer to "why do we stay," in my case, my therapist once told me that I was "in thrall" with my AH. So, frankly, I had heard that in the context of mythology and fairy tales, but I had to look up the definition:
Definition of THRALL
1a : a servant slave : bondman; also : serf
1b : a person in moral or mental servitude
2a : a state of servitude or submission <in thrall to his emotions>
2b : a state of complete absorption <mountains could hold me in thrall with a subtle attraction of their own — Elyne Mitchell>
I suppose that explains it to a degree. I have asked your question to myself a million times and have not yet figured out an answer.
Last week, I attended my uncle's funeral. It was SO GREAT to be with my family, because we are part of a mutual admiration society, and being with them just makes me happy. So in spite of sad circumstances, I did have some great conversations with my cousins and aunts.
They know of my situation, even though I hardly get to see them. One cousin said to me after she asked how AH was doing (subtext: how's the drinking going), "Boy, you took til death do us part literally!"
Then, when I went to say goodbye to my aunt who was leaving (it was her husband who had died), she literally grabbed my hands and said, "do you regret staying?" I mean, it kind of came out of nowhere, and I had no answer, and I still don't.
I love my husband. He's a huge jerk when he's drunk, but a fun and loving and wonderful guy when he's not. And my family represents the principle of math that two negatives = a positive, because my children are absolutely wonderful, responsible, caring, with-it human beings. So I'm not backtracking on that. Maybe if I regret anything it's my own lack of gumption with regard to behavior that could have actually helped the situation instead of just going along with it.