I have wondered the exact same thing at times. I have had a few friends who have had to come out as gay. Some of them were married with kids and got married to try to "cure" themselves. Finally they admitted to themselves that they were gay.
In someways it might be similar with "poly" although there is also an argument out there that says deep down we are all "poly" but because of social and cultural and conditioning reasons, most of us don't "come out". Still not sure whether there is truth to that or not...