There are many reasons, one of them being like what the other commenter mentioned, the likelihood of sex, but another one may have to do with sexual fantasies a

There are many reasons, one of them being like what the other commenter mentioned, the likelihood of sex, but another one may have to do with sexual fantasies as well? Maybe they like the other person believing they are a cheater? You can't assume that the target audience of this site is the ONLY audience simply because they advertise to "cheaters".