I would say most people look at the prospect of poly relationships in terms of monogamous relationships, and yeah I would expect there to be a wildly different dynamic in play for making it work with more than one partner, particularly under the same roof.
Most people look at relationships in terms of some very rigid ideals that were set millenia ago, and even though our society is changing at a breakneck speed, we're all still pining for the romance taught to us in movies and stories written centuries ago.
I think there is still a real place for traditional relationships, they are wonderful actually, but I think if we're to learn anything from people exploring multiple partner relationships, it would be that your relationship can look like a lot of different things, and no one pattern is perfect for everyone. What matters is you're with someone or people who make you happy and not longing for something else.