The women who stay have been abused, emotionally, the affair itself my not be classed as abuse but what follows is.Similarly I can't get my head around women who stay-having seen what cheating men do, the absolute disregard and lack of respect for their partners- they know they're hurting them, yet they do it again, and again, and again. Everytime they contact that person, kiss them, hold them, have sex etc, they're actively making a choice to cheat, some for years on end. That's not how you treat someone you love and respect. I could never get past or forget that, it would always be in the back of my mind, once that trust is gone. And it's so unfair that typically it's the wife/girlfriend who's life it goes on to affect- still thinking about it years later etc, yet he really has no consequence- keeps his family, his home, his status, keeping up appearances- that's what I think is so unfair- the partner did nothing wrong yet has to pay for it! Brings me back to my point that affairs are complex, as are the reasons for cheating, and the reasons for staying.
The gaslighting, the your crazy comment's, your this, your that. I'd say most do leave eventually but much like people who suffer domestic violence (they get the same questions) why don't you just leave, do you not think if it was as easy as that they would? When you have been emotionally abused to the point that you think there is no other option, you stay.
Anyone who partakes in an affair with a married man/woman is part of that abuse.