Yes, I misspoke, I didn't mean genderless pronouns were predominant, rather the male gender pronoun only is predominant. What I meant was there is no consideration of gender, using only the old standard pronoun for everything (he/his). Not saying these are deliberately excluding female readers, rather no attempt is made to not seem exclusive at least reading the language used. As far as that goes, I've never seen 'genderless' pronouns used in anything, not even RPGs.
Gotcha.
to sum up your observations outside of RPGs in non-fiction:
Nobody seems to use "they" or other truly genderless pronouns
every book seems to use "he" or other male pronouns
I think it is reasonable that just because a book only uses male pronouns, that does not mean the book or author is sexist/voicing a sexist position
So I doubt there's ill intent in these (or other) books.
The muddiness comes when somebody point out that a more inclusive practice exists, it is very risky to protest it.
I'm not sure why the non-fiction industry hasn't been hit by the "you're being sexist or exclusive" bug yet. But I did just think of a theory.
Pick up a how to book. Pick up an RPG book. Which book, or even which topic do you REALLY care about more. Enough to participate in online discussion forums, etc?
Odds are good, it's the RPG. There aren't fan sites for how to books. Other than the guy with a broken sink, nobody gives a rat's arse about
Bob Villa's How To Fix a Broken Sink book enough to form a website discussing it, let alone discussing shortcomings in the writing style. It's a tool. Not a pastime or passion for anybody. Once steps 1-9 are completed, the sink is fixed, the book is closed, and no thought or recollection is given to "how come all the examples used the word "he" instead of referencing women who might also have broken sinks.