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The trouble is that so many witnesses are simply not active, and that the top 20 can override the rest, and that the top 20 are basically centrally chosen by a few powerful accounts. This is my understanding.

So, why are the witnesses not paid, compensated, for hosting, serving, witnessing, seeding, mining, or whatever we may want to call it, unless if it doesn't include any, some, or all of these terms, words, especially the word "Seed," which we can understand is a conception bit torrenting, and the word "Mine," which we can get from Bitcoin. I would love to mine or seed Steem. If I was paid to be active, to seed, to host, to serve, to witness, etc, then I would be as active as possible, because the more I helped Steem, then the more Steem would help me, right? Is Steem not doing that? Bitcoin does that, right? Why would Steem not do that?

you get paid as a witness but it depends on many factors
see here someone recently talking about it https://steempeak.com/busy/@felixxx/witness-costs

But why not get paid like through a seeding BitTorrent style system?

don't ask me
it will have something to do with the steem architecture
you'll have to read up on white papers and steeminc explanations and witness explanations to get an answer for such questions

most people won't bother to ask such
it is how it is
there will be an explanation to your answer
if it is sufficient I don't know
it won't change regardless

That probably means that better blockchain social networks will be able to potentially do better than Steem someday if it has not already.