Of the men I've known who appeared to be faithful, that is still in very loving marriages till death and both parties thinking each one was faithful, they tended to have a male that was not incredibly social with many friends.
Their wives tended to be their best friend and they didn't seem to have a desire for many male friends, they were also not overly ambitious, were not crazy about team sports and didn't favour public drinking in groups with other men.
Whether or not pack behaviour comes into mens promiscuity I don't know, but peer pressure and a definite fighting for the best looking girl in any given situation probably pushes these men to compete with one another.
The less competitive men seemed, more stable, more reliable, trustworthy and better friends to their wives.
So no I don't think all men do cheat, or all women, I think there are many men who are capable of turning down sex, but most of these men are the type for the boundaries to be set in place well before it gets to the proposition stage.
It is difficullt I should imagine being this type of man with strong morals and boundaries as there's usually quite a bit of flack thrown at them from alpha males of being under the thumb and doormats, when it's nothing of the sort, they just respect their wives, through friendship and love. To be a stand alone man with peer pressure from others is I imagine difficult in a man's world, but these men as they go into old age seem to have the best of family life, respect and love of the wife, children and grandchildren.
You can see the one's who have done it right, not all men are shits.