Why do men have mistresses, visit courtesans, escorts, call girls, working girls, prostitutes etc etc? What drives them to lap dancing clubs, buy magazines and watch porn?

I think that there are a couple of dynamics at work here. Some men indulge because of an unsatisfactory life at home. How many married men complain that sex becomes a rote with no variety, the elusive BJ and general malaise sexually. In most cases it is not the fault of the poor wife, she has been caught up in the demands of the family, running the house etc. Some men indulge simply because of the thrill of the illicit, the frisson of excitement with an unknown woman, the knowledge that society views the act as unacceptable. There is also the element of being able to fish in waters that would normally be well beyond the norm. A man, no matter how ugly, old, fat, shy or under endowed can, with some selection be with stunningly attractive women who he probably wouldn't dare to even speak to normally. He faces little chance of rejection provided he is clean, polite, sensible and in possession of funds. Another reason for visiting may well be the possibility of indulging in activities that he knows would not be countenanced by his partner at home, this may be why we see so many politicians, business leaders being found in the arms of dominatrixes. There is also the ongoing debate regarding the genetic imperative for men to sow their seed as often and in as many places as possible. I don't believe that this bears on this debate. I think that it is simply the excitement, the pleasure and the ability to indulge.