I think this kind of highlights how no situation is best for everyone. I have a friend who has a "primary" and several "secondaries" and everyone involved is okay with this because they each fulfill what the other wants.
My wife is my "primary". We share finances and all of of the roles that a mono-married couple does.. except sex. We disagree on that, except for rare occasions.
She's got a few "secondaries" who fill the sexual and some emotional roles. I've got a few people who I'm not sexual with but who fulfill very different but no-less-important roles in my life. I wouldn't be the person I am today, and all of them complete me and compliment me in ways that nobody else can because they're ALL unique individuals.
I understand exactly what Cioli is talking about though. Nobody wants to be relegated to "standby". Yet at the same time, this is all some people want, or are willing to give given the relationship dynamics. And this is okay!