Swing is not the affair because both parties (husband and wife) both know each other, there is transparency.
Swing has an egalitarian nature, equal, fair (morbidly only men who have benefited, but women too). So the swing is not just a man's world. One Quote husband husband forced wife to swing!
Swing is democratic because all decisions are made jointly by married couples, there are rules of the game and who agreed with the consensus.
Swing accommodate basic instinct (basic instinct) individual men / women to want more than one and want another figure in the sex. So yes accommodate pent-up desire of polygamy / polyandry in each person.
Incidentally, swing it economically less expensive and technically easier than the practice of polygamy / polyandry. Because the relationships apply only during the swing meetings conducted. And that's lasted so voluntarily and morbidly binding. No commitment thereafter.
Swing may have more agregete and fishing adrenaline of being able to