Artists, writers, and inventors for thousands of years have known that, if not themselves wealthy, in order to pursue their muse they need a wealthy patron. Wealthy patrons are few and starving artists many, so only the most talented or profound find sponsorship. The lesser talents have to get a real job; the wealthy lesser talents indulge in vanity publishing. It's only in relatively recent times that marginal or niched creators have found viable markets for their efforts. And the Internet has made it even easier for such creators to market their wares, because the cost of production and distribution has dropped dramatically while finding a specialist market has become easier.
Musicians have always relied on a wealthy patron (a record company) to get their work leveraged commercially. Once wealthy themselves, many ditch the record company and seek to control/benefit from their creations directly. Those who can't find a patron in the first place are going online in droves, effectively vanity publishing their work but at very little cost to themselves and free to consumers. Those who strike a chord (if you'll excuse the expression) and find informal fame can jump to the next level and get a recording contract -- but in the beginning they actively encourage the free sharing of their work in order to promote their work. Think of it as an investment of opportunity costs in some hoped-for future return. And this despite the fact that in the music industry it is the recording itself (the expression of the idea) that has value.
In business writing it is surely the idea itself that is important; the expression of it (the published text) is less significant. If all you are doing is regurgitating old ideas and re-labeling old concepts, the text is all you have to sell, and with a bit of hype you probably can sell your books. If you are achieving conceptual breakthroughs with new ideas, you can probably change the world -- and your life -- but the words you use will be secondary to the concepts. That's why copyright is for the expression of ideas, not for ideas themselves. I'd rather produce one transformative idea in my lifetime than copyright a hundred inconsequential books.
Let me stress that I am not advocating un-attributed lifting of other peoples' writing at all. I believe in the value of protecting your intellectual property as far as sensibly possible: I have in the past gone to the expense of taking out several international patents for various software tools, and assert copyright of one form or another (mostly Creative Commons these days) on most things I publish. But you need to look honestly at what it is you are creating and decide how much of it comes from and belongs to you, and how much comes from and belongs to your world.
If creators jealously protect their words, they may condemn their ideas -- and themselves -- to obscurity. And does it make any difference in the world if a marginal thinker has the poor expression of old idea stolen by some other marginal thinker? Maybe, if you believe in the butterfly effect. Oops, maybe that's a copyrighted term. Better call my lawyer.