I wish I could articulate this better than I'm going to but......
People often want to make polyamory as close to monogamy as possible in some attempt to correct all the things that are morally wrong about it. Things like having sex with someone who isn't your partner in an exclusive, loving, committed relationship. These people know they desire having multiple relationships, or their partner desires having multiple relationships, but the only way they feel this can be done the "right way" is if everyone is involved with each other and the situation replicates a monogamous relationship of the traditional variety.
People who feel this way believe that monogamy is the ideal. They believe that a monogamous template for relationships is the only way to achieve "real" commitment. The absence of monogamy inherently negates commitment, in their mind, and they strive to compensate for that imagined deficit in their polyamorous relationships with "tools" such as couple privilege, unicorn hunting, controlling their partner's relationships, sex negativity and just about everything else I hate about polyamory.