Earlier quoted context omitted.
Because James Joyce's style isn't "simple" by any stretch of the imagination, I would guess? And the essay presents its position as a general statement void of all context. What context are we supposed to assume here?
Everything has context. Paul Graham is a leader in the startup scene so more than likely he's talking about the types text relevant to startups. Blog posts, press releases, etc. Again, why the fuck would you assume Paul Graham is talking about James Joyce?
I do not believe that the article's prescription is confined to business writing.
> Paul Graham is a leader in the startup scene
That is true. But Graham is also a self-described essayist. He was writing long before he started Y Combinator, and his essays often discuss writing as a thing unto itself. For example, his "Nerds" essay mentions that one of his goals for life in high school was to write well^2.
Given that Graham is deeply interested in writing, and that the article doesn't explicitly confine itself to business writing, I think it's quite a stretch to assume that this essay is only talking about business writing.
> Again, why the fuck would you assume Paul Graham is talking about James Joyce?
This is a strawman (and also unnecessarily combative).
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[^1]: Well, see my top-level comment. But that's not really relevant to this comment.
[^2]: "There was something else I wanted more: to be smart. Not simply to do well in school, though that counted for something, but to design beautiful rockets, or to write well, or to understand how to program computers. In general, to make great things." http://www.paulgraham.com/nerds.html