fearless:

Here is a list of reasons why peopple cheat:

Why Men Cheat
The most frequently cited reasons for infidelity among men include

more sex (the desire for a more active sex life)
sexual variety (a desire for different kinds of sex)
opportunistic sex ( taking advantage of an opportunity to have sex without the fear of getting caught)
to satisfy sexual curiosity (about a specific female)
a feeling of entitlement (the belief that it’s a man’s prerogative to cheat)
the “thrill of the chase”
the desire to feel important or special
sexual addiction

Why Women Cheat
The reasons most frequently cited for female infidelity include

a desire for emotional closeness and intimacy (someone caring to confide in and bond with on an emotional level)
a desire for attention (wanting be the center of a man’s attention again)
to reaffirm her desirability (To feel validated as a woman)
to re-experience feelings of romance
a desire to feel “special”
boredom
loneliness
sexual excitement

To me these sound an awful like people getting their need met elsewhere.