I asked what is that reason?
Well naturally she said because one or both people feel that there is something better out there.
Oh so the grass is always greener?
But what about those people that do stay together with the very first person they were with. Are they just lucky or dumb? What about those people that are in arranged marriages and are very happy? Are they just lucky or dumb? What about all the single people that don't have someone? Are they just unlucky or dumb? Or maybe smart?
I struggle with the multiple partners concept because it just doesn't make sense from a scientific standpoint. At the same time, it makes sense that one of the partners, or perhaps both do not posses the skills or brains necessary to make it work.
Fate? Destiny? Things are just meant to be? I don't think so. I think if you have two people willing from day one to grow together, be together, and are committed it will work out. I also think the smoke screen of courting messes things up. "He was so nice and sweet when we dated, and now I hate him". Well that's because you focused on him focusing on you, rather than focusing on who he really is. Get it?
So while you are in the buffet line of life, picking and choosing between new mates, try a nicer restaurant instead. You'll find the nutrition you need, and then some. Make the effort.