why people cheat sex?

it is the survival of the species. gal n guys are created to make sure that mankind don't become extint on the earth. so all are created to have as much sex as possible with as many diffirent people as they can. so that they can make as many babies as possible. but there is a mis calculation in the natural process we had over produced. but any how as happened in Japan the population is shrinking now. it could be that the natural process is working.

You should provide a little more detail, cheating as in married and just sleeping around or something else? Regardless, some people tend not to be satisfied with what they have and always go looking for something better. It's that whole grass is greener thing, if this is the case then cut them loose and move on, you never know what they may bring home. Others, well they just cannot help themselves. It's a psychological inability to saying "no". Either way you're better off without them.