Because it's there?
Man marries girl he loves. Girl says she loves him. Man is seen by girl talking with other girl. Mans wife upset and accuses man of philandering. Man tries to ignore it. Wife insists man is philandering and makes mans life miserable. Man has two choices, either philander or divorce because man can't live with angry girl. End of story.
A person needs to feel loved. Thus picture a love tank if you will. If it is full, there is no desire to look elsewhere. To keep that tank full, one's spouce should know how to express love to their spouce in a manner that they acknowledge. Thus one needs to know their spouce's love language.
There is five basic love languages.
1. Quality time
2. Acts of Service
3. Physical Touch
4. Words of Affirmation
5. Gifts
Usually a person has one main love language and possibly a secondary love language. If you are not doing the love language that is recognised by your spouce as love, you are wasting your time.
The trick is to determine your spouces love language, and if you care for them (and you should) you do their love language and "fill" their love tank full. Thus they feel loved and don't think of other immoral means to try and substitute love in their lives.
Example: if one's spouce's LL(love language) is quality time, then you need to turn off the tv and spend time with them one on one with your 100% attention. The crave it and it speaks love to them.
But.... if one spouce is not a quality time person and the other spouce tries to express love with such, they will in effect smoother that person and acually obtain the opposite objective. I am not a quality time person, but my wife is, I know I have to take time to express my love for her by giving her special time, she needs it to feel loved.
If ones's love language is "Words of Affirmation". Then a word or two truthfully express about how good they do something makes a world of difference. This is my LL and my wife does a good job of telling me how proud she is of me because I do certain things for her and the family. I could live a good week on an Honest good compliment.
If ones's LL is gifts. You will notice they are usually the ones that are constantly give you things. You know the type, you can't outgive them. They do it cause that is what they know as expressing love to others and they need a small token of love expressed back at them to feel loved. They are reaching out when they give. You con't have to outgive and it does not have to be something expensive, perhaps an extra icecream cone when you go to the store. A little trinket that caught your eye that you know they collect. Just something... says a whole lot of love to them.
Perhaps their LL is "Acts of Service". Then doing a chore for them every now and zen means the world for them. Perhaps jumping in and helping with the dishes will fill that Love Tank to overflowing. If they are overflowing with love, they just might be more than willing to do some loving back in a manner you appreciate.
Lastly there is "Physical Touch". Men ofter think this is surely what theirs must be. But often they are decieving themselves. Physical touch could be as simple as goosing them when you pass by them. Perhaps a bunch of hugs during the day. Yes and it could mean sex of course. But often men think this would be their LL, but in reality, if their true LL is "words of affirmation" and the wife is saying something like "when are you going to take that garbage out, you know it ain't going out the door by itself" then they often are so frustrated they are not in the mood to be nice back to the wife. One knows sex is a multy level experience and for it to be good, it helps not to feel empty inside. If your love tank is empty, then your sex is probable lacking also.
Take time to read your spouces LL and start expressing it. It's rewards are beyond a divorce.
LOW OiL
I am very lucky that I have a great wife and would never think of cheating, but, I have a friend or two who would be better off without thier hags, if not for kids being involved.
Actually, I don't believe there's any 'one' answer. Cheating, straying, fooling around, lust, outright fornication for fornication's sake, one-night-stands, etc can be on one side. A true affair of the heart, for many reasons, can be on the other.
I thought this cobined with "misplaced anger" sounded like a popular theme. In the standard relationship outside of marraige I've seen women from broken homes intent upon ensuring that their relationships following the same pattern they were familiar with. "If it ain't broke, break it" tends to be the thinking in this area. My word to any male or female when entering a serious relationship that could head for marraige is to simply observe what is taking place currently in their family, because that's what you'll bring into yours.
My best friend ignored this advice about his wife. When they were dating and we were all friends, here pattern was that she always spoke about how she "hated" her family and so&so was this, so&so 2 was that and Mom & Dad were "the-word-of-the-week". The advice "Dude, she's a psycho" didn't register with my buddy. I explained it to him thus :"She runs to you as an escape from her family and confides in you. She spends her time with them in close proximity and their combined personalities are so disfunctional it creates the hell she lives in from day to day and describes to us. Guess what? She eats and drinks misery on a daily basis! Ever think what will happen when you take her out of that environment and bring her into a confined area with yourself? YOU BECOME THE TARGET OF ABUSE!"