And cheating for others has saved their lives. Literally!
We stay in marriages bec society deems it correct. Divorce & the acceptance of it in our generation is fairly new. 20-30 yrs ago "people didn't get divorced." Did they love each other more then?
No, they accepted their miserable state bec it was frowned upon by religious sects, history & current society.
Less than 12% of primates are monogamous. So where does this ultimate pressure come from that we have to stay married or it's bad?? Just look back in our history