So many reasons
My husband was abusive (mentally and physically). He has no respect for me, emotionally is not there, we're always fighting and yelling, there is no control over finances, and the list goes on. It was this way for at least 10 years if not longer.
We were married for 15 years and have known each other for almost 20 years. I thought after all this time we would be able to work it out but it doesn't seem that way.