I think there are many reasons and this is just one marker of general education decline in the US. Chrystal's 2 volume Algebra books could hardly be completed by first year university students nowadays, and they are from the turn of the 20th century. I had an American high school physics text from 1948 with dense text, math formulas, and nicely hand-drawn illustrations that served me well in 1976 a few years before I went to High School. By the time I went to university, textbooks started to put in a lot of photos, diagrams, marginalia, and tangent facts, or distractions from uninterrupted development of the ideas students are expected to handle. The shift from books my mom bought me, like The Boy Engineer, which was filled with optimism and enthusiasm for engineering throughout the ages gave way to texts filled with impending disasters, pollution, chemicals, plastics, expected zero-risk in all things. Russian math books are rigorous and thorough, and I have found Indian science and engineering texts to be good for their explanation and continuous development of the core idea, and relevant, graded drills. I have 5 kids ranging from 7 to 29, and I the American text books I have perused for them have become massive and bloated with too much tangent material, distractions. Let's see for my younger ones. They mainly do all work at school, not much homework, and texts seemed to be endless worksheets coming from newsprint workbooks that spread the main point across pages instead of paragraphs. Math is OK, but very segmented, but at least there are some word problems or contextual exercises to get them into applying the math. Let's see when they hit high school. And although I had a Commodore PET 2001 in 1977 with 8k RAM (later 32k upgrade, tell Sam, I know the value of RAM!), a cassette drive, and Commodore BASIC in ROM, I am not a fan of the screen vs. teaching and books, or boards (whiteboards, or screens). I also just watched, "Good Luck, Have Fun, Don't Die", so this is some fallout... Going to first principles is sometimes a big ask, but skipping everything after a Google search, and deriving a small part on your own is not the way to hypertrophy of the brain. I started looking over the first 3 chapters of Euclid's Elements (Greek on left, English on right, and diagrams) and started to work on it with hopes of dragging my 7 and 11-year-old through some exercises to teach them thought processes in looking at and solving a problem. Then again the Russians faked an advanced fighter/bomber MIG-25, and this pushed America to develop the F-15 in the 70s. It turned out the MIG-25 was heavy (built of nickel steel), hand riveted, and vacuum tube based! I guess you can't judge a book by its cover here.