There's a trope that works it's way around poly. It usually winds up going something like this: "You can't expect one person to meet all your needs, because it's like...you love your parents and you love your friends. But not in the same way. So it's natural to love more than one person at a time."
Putting aside my already stated opinion about having one person vs. many people "meet your needs" (again with the "needs" thing - it's like a tiny irritant at this point). There's something specific about this argument that I disagree with. It's the idea that poly equals purely platonic relationships with others. Not that there aren't people out there who really are just looking for the friendship/romance aspect with other people and not particularly the squelchy bits, but just in my own experience and in my own head I don't see a lot of people going through the communication, the rules set-up, etc. etc. just so they can have a few buddies to hang out with. What does that look like? "You can take them out to the movies, but don't bring them over for board games?" Maybe there's a bit more to the whole idea of "emotional" cheating somewhere in here and that's what I'm missing. Having been the friend dumpee a few times (i.e. somebody who is told by friends that I can't hang out with them anymore because their significant other is somehow threatened by the outside "relationship"), I guess it makes sense in a sort of standard narrative way for people to need to define and somehow protect themselves against platonic things that might turn into something all gooshy (or, perhaps more frighteningly, squelchy?)
In any case, I don't agree with it. Unless we're getting Oedipal about it, of course you don't love the people you're entering into relationships with the same way you love your parents. Of course they meet different "needs" for you. Trying to say the way you form consensual adult relationships with other people is similar to the 3-year old idea of sharing your toys because it's...you know...just what one does is sort of simplifying the whole thing past necessity.