The simple truth?
I have known/felt monogamy wasn't for/didn't make sense to since I was a child. I could never combine society's rules and ideals with my feelings. For a long time I thought this meant that I should not/could not be in a long term relationship. It has only been within the last couple of years that I found my feelings were not unusual and that there was a word for it.
For some people it's an option but not necessity. For others it is only with or because of certain people that they choose this path and for others it is ingrained in who we are. There are a lot of different paths and ways to be poly, not one way suites everyone.