I wonder why publishers seem to lean towards 500-pages books. Very complex ideas have been expressed in 10-page articles, spreading probably much smaller amount of information across hundreds of pages does not help.
While I agree with you about the observation that many non-fiction books seem unnecessarily padded with filler, I think it’s because otherwise the book looks physically inferior and/or would be expected to cost less. And they’ve decided that this is the page count that optimises sales, instead of optimising reader satisfaction.
If someone’s at the book shop and see a bunch of one-inch thick books and a small 20 page pamphlet, they’d expect the pamphlet to sell for a fraction of the price. Or be tempted for the thicker book because “the author clearly did more work.”
I have the same feeling, however personally I'd prefer thin book to a thicker one even for a greater price in most cases, mostly because I just dont have enough time/stamina to dig through graphomaniac texts.
If someone’s at the book shop and see a bunch of one-inch thick books and a small 20 page pamphlet, they’d expect the pamphlet to sell for a fraction of the price. Or be tempted for the thicker book because “the author clearly did more work.”