This is sad, really.
I think there are multiple factors at play, but one that I believe is crucial is the abandonment of marriage as a covenant, specifically a covenant before God. I would guess the vast majority of marriages have difficulties. Occasionally you hear of a couple that never uttered a harsh word at each other. My marriage is certainly not one of those! But when all else seems futile, I fall back on that covenant. And part of that covenant is being faithful and not having extra marital affairs as even Jesus himself stated that adultery is a valid reason for release from that covenant in His sermon on the mount.
I would be quite lonely without my wife.