Here you are, entering the prime of your lives, and you're remaining with just one person. Why? Why sacrifice the variety, the possibility of something greater, to pusue a romanticized ideal?
You've never walked by a girl you're attracted to, wondering just what exists in that mind of hers? The personality, the intelligence, the chance that she unlocks something in you that your current partner doesn't.
I'm of the mind that people who submit to monogamy are those who fret at the thought of being alone.