I was thinking about replying and decided that there was one aspect I can disagree with, at least in the way you portrayed it. I have a similar way of looking at most of the things you mentioned and don't understand the 'completing the picture by adding people who satisfy this or that need/want of mine' concept that well myself, as it doesn't apply to me, but I think that there is one point I can relate to which is definitely different for me.
Yes, I think that you are right, no one will die because he/she doesn't get sex with other people. No one will die because he/she isn't able to express their feelings for others (yes, I know this is a different level we are talking about now). And now comes the but: It's damn unhealthy. As far as my personal preferences go, no, I would never have gambled my marriage because I wanted sex with Lin. Never. But I was unable to disregard my NEED to express my feelings. It made me sick. It turned me into someone new, someone I wasn't able to cope well with. And I believe, that in those cases where it's about polyamory, forming relationships, expressing love for different people, it is a need, not a want, to be true to those feelings. Because just like not eating and not drinking it lowered the quality of my life to refrain from being true to myself; of course, I would not have died, but it would have greatly affected my life, my marriage/the persons closely involved with me and myself. And I think it is reasonable to regard this level of possible change and effect as more important than the craving for some fleeting moments of lust.
You are right, poly should never be a means to any end, but there is a strong core in poly that isn't self-serving in and off itself like there is a core in mono that is absolutely pure without anything negative: Expressing the love you feel. That's all. As long as people do that and whatever relationship they end in with this or that approach, it is possible to need or want more with time, because as long as you love your spouse or partner you will look out not only for your personal needs and wants, but for his/hers as well. At least that is what I believe in and what we live right now. And there is not one 'dead element' I can think of in our life because of the relationship structure we choose or found ourself in, in the end.
Everything can be handled inappropriately. I don't think you should judge the way you see some people practising poly as the way poly always is. Because that can't work, as there are so many forms out there and many are not as dysfunctional as the examples you mentioned here. (I am sorry if I missread something or interpreted anything the wrong way, that were my initial thoughts on the matter.)
Facts: 30, female, bi, v-type relationship with Sward (husband, straight, mono) and Lin (boyfriend, straight, mono), poly-fi and co-primary.