I was miserable for years with increasing emotional and verbal abuse. He was also miserable but lashing out and taking it out on me. Even though he wrote me a letter in the summer before I left admitting he was an asshole etc and wouldnt blame me if I left, when I did he was shell shocked and didn't think I would do so.
2 years on I am much happier, but I was miserable with him for years (not the rest of my life, that was fine). Why didn't I leave him? I thought I loved him, didn't want to split up the family, worried about finances but most of all the fall out that would occur afterwards. It happened but I managed to try navigate it as best as I could. There was no one else, although I did start noticing that men do indeed treat their partners nicely, and I was missing out on a loving affectionate relationship. We had moments when we were happy, but on the whole it was a mismatched relationship and there was no balance or care about my needs. He just simply didn't "see" me anymore. He was so wrapped up in himself, and after kids, work, him, and everythig else I was way way down the list in terms of getting my needs met.
He would never have left me, because not only did I work and he didn't, I did most of the wife work type stuff, guided him as a parent and tolerated his fucked up family and views on life. He is totally lost without me. I don't even think if he decided to have an affair he would leave me, because he had it too good.
I think now its more common the woman leaving the man, because generally its easier to do so financialy than it was 50 years ago. 50 years ago most mums were stay at home parents and had finances controlled by the man. Now women are much more independent and a lot of women work AND do all the wife work, so if it feels harder being in a relationship than not, they can leave.
In my experience with my friends and family, its the woman leaving the man, and in most cases its because the women were just fed up with doing everything and taking shit at the same time. I only know a handful of people who left because of affairs, the wife or the husband (that I know of). My ex tried to jump straight into another relationship because he needs guidance and feels more secure when he has a woman looking after him. He has had several flings, and I can see he places so much importance on that. He hasn't learnt to be happy in himself yet.
Now I still do everything, but I also get some time alone and for myself when he has the kids, I never had a spare minute before because he didnt think I needed it or it was important. He even used to kick off if I went to the gym on my own for an hour. That was my only me time all week.
Anyway, the most important thing to me in the end was to have my autonomy back. I have that now, and for me that is more important than anything. I am now with an amazing guy, who respects my independece, looks after me, "sees" me in a way no man has ever done so and lets me assert my own autonomy. Not one where my needs came bottom. I cannot see myself living with another man in the future, I'm fine as I am with me and my boys.