I disagree with this premise. Because Sex happens, does not mean that sex is "the priority". Evidenced by the fact that Homosexual relationships also feature "Sex". Further evidenced by the fact that.. even without females or other males.. Men still have a compulsion to ejaculate... which is why the porn industry is so profitable.
So.. minus that premise, and injecting a bit of humanity.. your question then becomes:
Why would a man desire to be with a woman?
It depends on the man and the woman. There are many different needs that we fill through relationships with others. Most of those relationships are not sexual.
So there are as many answers to this question as their are individuals.. but if this is a real question.. you can find the answer
in your own experience.. by analyzing the non-sexual relationships you have with women. For example.. your sister.. your cousin.. your classmates.. your co-workers.. your mother.. Destee.. to name a few.
-Context is everything.