Maybe the reason is that "a woman's heart more tender male"? Perhaps some element of truth in this.
But I think the main causes of still others. The behavior of people, especially on their psychology greatly influenced by established habits, thought patterns. It has long been the custom that a married woman - homemaker. Its mission - to save it at all costs. Even if they have to step over the wounded pride, forgiving "treacherous apostate."
This is due to many reasons, primarily physiological. Of all the mammals, the human baby - the most vulnerable and defenseless. He needs constant care, attention and protection from their parents, especially the mother. Many hundreds and even thousands of years, a woman gave birth to a new essentially provided in the literal sense of the word "tied" to it. Of course, it is at this moment particularly heavily dependent on the husband-breadwinner, and willy-nilly had to forgive his shortcomings. Even taking the most rude and intolerant forms, including harassment, beatings, treason. Times, of course, now the other, but the historical memory - a powerful thing.
It is necessary to take into account the fact that initially the public attitude to male and female infidelity was completely different. If playboy husband-honored only restrained conviction, the unfaithful wife incurs the most furious anger. Moreover, it could incur severe punishment, including the death penalty. And until now, such a situation exists in some jurisdictions.
We should not forget here about any circumstance. Again, historically happened that for men cheating wife - not just bad luck, but also shame. For women, cheating husband is a huge disaster, but not a disgrace that fell on his head "shameless sovratitelnitsy." She is psychologically easier to be generous, forgiving an adulterer. Especially, calm yourself arguments like: "But he did not stay with her, he realized that I - the best that I do not have anyone better! "And thus further improve their status in the eyes of the public as a tireless and patient toiler guarding precious family home.