I don't think one can find any reason to justify it or accept it. Be it the man or woman.
And there may not even be ANY reason, some people may do it just because they have the opportunity and encouragement from other person.
Yes, just because they have a perfect opportunity.......... and fall in to emotional trap and **have no strong belief **in either not to go in to the situation or fool themselves of being able to resist.
Lack of attention, love, sex, satisfaction or whatever are just fake reasons people may come up.
**If someone WANTS to cheat, that person WILL cheat no matter how much that person is otherwise getting great sex, love, care or attention or thrill at home.
i am not a female but i have listened it so many times from different people that the main and most important thing among any happy couple is their strong sexual relation. and if either one of the partner is unable to give satisfaction to hir/her partner that always bring distance among relations. and most the time people start to ceate so many reasons to justify their brokeup. as they cant say in public that what is the main reason but all of the showen reasons can easily be managed if they have mutual understanding and love among them. i mean one can compromise on so many things for the sake of love. and this compromise is not pain at all.
some of the couples who are unable to take that step of breaking relation as this is a big taboo in our society those particular people sometimes loose their control as this is big need.
i know there can be other reasons like some people only do for the sake of fun and some have oppertunities. and money can also be a reason.
but the main point was if a man or particularly a women have all the satisfation in her bed then i dont think that she will leave her man.