I don't think sex is a reward for the man in most relationships. That's not how it works. Marital relationships are much more complicated than that and very varied.
Do you really think life is this simple? What I see is men do things that they were taught to do to funcion in a given society, things they need to do to survive, things they like doing just for themselves (a very good motivation) and occasionally also things to look good in front of women (not necessarilly theirs). I think in most marriages men display a mixture of behaviours the woman likes and dislikes (sometimes even hates). Despite doing things the woman hates, a man can still often have sex with her either because she also sees the good things, she wants sex and is willing to overlook the bad things or she has no power to choose otherwise... life is really complicated. If men did only things women liked, the world would be completely different.
I mean, at the end of the day the wives either approve of their husbands actions and reward them or don't. To them, it's better to be with a man who gets paid to kill little girls than one that doesn't. That's why they're with them, lol.
Yeah, it really is that simple. Sorry you're trying to overcomplicate things.
I think your 'oversimplicity' argument would hold more water against those saying it's just the men of iran who are to blame.