I love my spouse more than anything in the world. She's my all. She's my reason for being. My father was an incessant cheater. He always cheated on my mother, and eventually he left her for some other, younger woman. He's still with the last woman, but there's an emptiness in his eyes. He's not the man I grew up with as my father.
Some people simply go through life unable to appreciate where they are, what they have, or what is important. To them there is always something better. It's so much easier to walk away and start anew than it is to man-up and face reality and all the problems that go along with it.
That's why some people dislike their spouses.