I think when you are connected to someone, truly, you only want to be connected to that someone, then you have no need for others. That if you are in love with someone you can only been in love with that someone while you are in this state, anyone else won't. I remember I was in someone's back garden and there were people there, other guests, and there were guys there that to me looked nice, were nice and the feeling then just hit me as the hours passed. That the only person I wanted to be there was the one I was in love with. And it was a moment when I understood I was falling in love with this other guy. That he was in color but the rest of the guys were black and white. I missed him there. He was to later become my first boyfriend. To me that moment was such a realisation. That I knew for a fact that these were some really nice people, guys, but something about me had changed. I only needed him there, he who was in color =)

It is usually them I think, I don't know but I can imagine, that have rather superficial relationships because they themselves are superficial that are fine with having multiple partners at the same time. Or could be someone is looking for a connection but have lost it or not found it with it's current partner and crave it, but usually then the moral codes step in sooner or later and you don't want to be in that situation or cause that situation for someone else. Just my thoughts.