Why does this guy that I know, stay in a romantic relationship with his wife, if he thinks she is a bitch?

I don't understand the logic. I know this guy that is always telling me that his wife is a bitch, yet she is still his wife. He always says it with a smile that she is a bitch but you can tell he actually thinks it. He says how she has an attitude, etc. Always telling me these things. He says he is romantically in love with her still but who knows if he is in denial.
Why does this guy that I know, stay in a romantic relationship with his wife, if he thinks she is a bitch?
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