YOU WERE CAUGHT CHEATING-WHAT’S YOUR EXCUSE?

I always wonder what makes people cheat on their spouses, irrespective of sex. Most people would conveniently say absence of adequate attention, unfulfilled sex life, financial imbalance, sudden change in appearance/attitude of the spouse.
However, if we look around properly, we might likely see a few cheating spouses who do not have any of the above as an excuse. It now bothers to say, what could be the reason for cheating? Sincerely now, if we did not have religion or morals, how easy is it to be with one person continuously for a long period of time? You wake up with the same person every day, eat with same, come back and sleep with same.
 Could it simply be the human nature for desire for something new? Or just a greedy nature? Maybe lack of trust? If it is the non-sexual cheating, it is very likely to have one of the already stated excuses above as a reason. However, for the sexual cheating, one wonders as it still all boils down to one thing- penis goes into the vagina-just maybe from various angle.
Maybe I am missing something here. Otherwise, it could be safe to say some people just lack morals or they are sex addicts. Trying to split it now, for the female, the male organ naturally should feel the same within when erect no matter the size or shape and as long as orgasm is attainable, there should not be any reason for sexual cheating.
As for the males, hmmm, truly? I cannot pretend to have the full understanding of that. It's crazy right? Think about it though, what separates us from animals? The ability to have a choice and decide what is right or wrong. We cannot throw morals away and snatch silly excuses when we do wrong. Whatever the reason, I believe for a communicating couple, it should be attainable between them if they really try. Or could there be some things communications cannot change?