There are more women than there are men, and whether you know it or not, "your" man probably has another woman...or two. Stop being naive to these facts. A man has to both love and be in love with a woman in order to be faithful. Majority of you have men that only love you and that's makes all of the difference.
Most men are not in love with their women. I am using men as the end all, be all because society is patriarchal and it is fitting and very true for my assessment.
Do you ever, ever hear men saying "I can't wait to get a ring!" or "I can't wait to get husbanded up!"? No. Most marriages are initiated by women as are most divorces. Society has convinced most women that the pinnacle of their existence revolves around marriage to a man and bearing his children.Because of society brainwashing most women this way, men can generally get away with whatever they want to because they are the prize in the relationship, not the woman. What a lot of women do not understand is that they are nothing more than live-in maids, cooks, and sex partners. Of course a man can love a woman who cooks, cleans, and fucks him. But the magic is with the man BEING IN LOVE with the woman. Love and being in love are two different blurred lines and people like to gloss of this fact in order to save face and their feelings.
I think that infidelity is rampant because most men are not in love with their women. I could also argue that forcing most people in monogamous relationships also creates infidelity, but I do not feel like explaining all of that right now. Anyway, yes, the "being in love" part of relationships do not last long at all. Do you ever hear people say "The spice is gone"? or "I'm bored in our relationship"? Yeah, that's where these sayings come from.