Yes, micros~1 can do all that, but that doesn't mean the FOSS community has no leverage. Let's start with noticing that even with micros~1 providing their own training materials there is still a substantial market for second-source courses and books and whatnot.
I was in the local public library not too long ago, and upon inspecting the "computer" section found a case full of office 2000-through-2007 and windows 95-through-2003 and word something to whatever and powerpoint this to that and ... well, you get the idea. There was half a shelf of vb, a couple ceehash and maybe one C++-on-windows book. Oh and a sack of books about third party windows programs, all versioned.
But nothing about even the for-children fundamentals I recall from the home computer era. Or anything vaguely interesting beyond using that one brand magic box as an appliance of this kind or another. Alright, there were some clearly lost linux-y books about, but that certainly wasn't the bulk. Between them those few books did have more actual content than the rest of the bulked-up-with-screenshots computer-y books.
I think that this, while saddening and an insult to trees, is a fundamental weakness in the redmondian+bandwagoneers model. Because those books ain't free, either.
There is a market for FOSS books, just look at all those books O'Reilly puts out. Those often aren't much more than glorified cookbooks but then again sometimes that's what you need.
And, as a final point, the FOSS communities depend for the software on its programmers contributing code. What's to stop people who don't code but want to contribute anyway to try their hand at writing documentation? It involves trying things out, asking questions, then writing something at least slightly better than the usual and nearly content-free "tutorial blog post". And the result is a suddenly far more usable program. Even just from documentation writers asking developers critical questions like "what does it even do there?" and "but how do we use that then?"
I know that at least the FreeBSD project has long put efforts into gathering up that sort of thing and integrating it into "The Handbook" and "The FAQ", to reasonable-to-good results, even though the most of more recent contributions could use some serious copy-editing. But that's just more contributing opportunity.
The important point is that the mere fact that documentation is available at all is very noticeable. The *BSD family has always had pretty good manpages, and even the linux guys are catching on to that now.