Mine had several reasons, which could all be narrowed down into three categories:

Living situation
Personality conflict
Celibacy

A friend suggested I could get the marriage annulled instead of going through a divorce because it was never consummated, but there was more than just the lack of sex involved, and I wanted it clear that I did spend ten years of my life working on it. I could never explain away ten years of my life as "it never happened". It did happen, and it shaped many of the rules and standards I have now.

But, yes, I'll admit, the celibacy was the biggest resentment I had during the whole thing - more so than finances, his passive-aggression, and my wrong choices.

It wasn't a marriage, but I did break up with a boyfriend over it. I cared about him a lot but felt I needed to explore. I still question whether I made the right decision sometimes though.

Yes, when I was younger, and I did leave him for it. His lack of interest in sex with me caused my to find comfort with one of his friends- it wasn't the smartest decision on my part, but I was angry and sexually frustrated.

What made it worse was that he would blatantly check out other women and make explicit comments, which usually never bothers me. However, it got to the point where I would be fishing for comments and I would get nothing except maybe, "why are you wearing a dress?" I didn't understand what I did wrong, and I felt so insecure about it.

Our sex drives were completely off, I wanted it close to every day, where he would want it only once a month. There's nothing wrong with that, if that's what satisfies you, but it didn't make me happy at all. If anything, I felt unattractive and miserable- I felt the rejection was my fault.

Of course, from hindsight, it wasn't at all, and I should have figured out within the first few weeks our compatibility was off and I should have left him, instead of trying to "fix him."

Better to say there was a chance because of it, but then it got worked out with even more patience, and the reason to break up with anyone in my life was never that kind...