There are two categories of outside interest: physical and emotional. Physical is self explanatory, but for peeps that are too conditioned with social influence, its looking for attention, acknowledgment, romance, and affection. Emotional type is having someone talk, listen, share, sympathize, and support.
You can scream that you hate people who cheat, but you do it all the time...you just choose not to look at it that way. How do you feel if someone says you look good, smell great, or pays attention to some little detail of your existence? If you are normal you feel great. How about when/if they flirt a little with you? Your confidence soars and your behavior patterns will change temporarily. Guess what, you are emotionally cheating! Men and women experience this all the time with coworkers, coaches, trainers, store clerks...all kinds of interactions. I makes you feel noticed and important, even if it is only for 5 seconds.
Physical is SIMPLY that some people, both men and women, require it. Its how their body chemistry is made up. Not everyone is a clone and operates the same way. You may be able to go a week but your partner may need it every day. Simple as that.
So what do we have today in the world of a legal contract called marriage? We have one or both partners getting COMFORTABLE. This is defined by not talking much about emtional needs or physical needs. Men/Women that have needs are drawn to porn if partner does not need it much. Men/Women take a kid out to a class or practice and find a person that meets the emtional needs. Then there are the few that dont require either and are happy where they are (minority). We are not built by law, rather as another person stated, we are 98% monkey. Its natural no matter how unnatural society (law/religion) tries to make it.
I liken it to a person being in a desert for a year or fifteen years...then happens upon a glass of water. This water pays attention to you, compliments you, wants to be with you, talks, listens and actively supports your life. What do you do? If you hate cheaters, then you bypass it cause your COMFORTABLE with you misery and cant see beyond your containment (law/religion/personal belief). Most will consume the water like a savage beast! What is the person giving up at that point? You may need to look at yourself hard. Are you available and actively pursuing your partner daily to keep the challenge and interest? Do you fall in love with this person EVERY day? Loyalty is admiral but is it really attracting your partner to you? Just some thoughts :)