Really, I don't get the purpose of your thread. It seems like a rhetorical rant more than anything. I think you've been a little obnoxious in some of your replies when people have set out to try and answer the questions you've posed. You said you didn't want to know how the mode works, but you wanted to know how useful that was? Do you understand that this is subjective? For example, I find campaign useful because it allows me to play modes that are otherwise dead on this server! In terms of how I personally rate the modes, confront comes last for me - I'm just not that much of a fan. However, if it means that in order to keep playing a game that I like - I have to play some of my least favourite modes - then so be it
When Masternoob said that you get spirits from campaign, I'm pretty sure you know that he did not mean that this was the sole purpose of it. In my opinion, he has provided you with different things that you COULD find useful, if you chose to do so - but again, "finding campaign useful" is subjective. I also find your response to sodium quite naive where you said the following "only alt farmers have fun in campaign, by spoiling somebody else's gameplay". It's clear that you don't enjoy the mode, it's fair enough that you're asking for personal or practical reasons as to why campaign is "useful" - but I think that you should try being a little more open-minded in your approach. If you're just going to easily dismiss people's responses in what comes across in a patronising and arrogant way then why do you expect people to answer your follow-up questions when you haven't even treated their initial responses seriously?
I find playing in a party during campaign to be great fun because I usually have a reliable team who enjoy these modes and I find defeat, destroy and capture thoroughly thoroughly enjoyable too (I will admit that I find defeat the enemy leader quite panic-inducing!). Basically, find whatever you want to be useful - or don't, lol.