Well, when I was a kid in the 80’s, almost all of my textbooks had been recycled from the year before, and all of them had been drawn in, scribbled over, ripped up, had jelly stains on them - the school district replaced them every maybe five years or so, so every once in a while, I’d get a clean one, but usually I’d get something that was useless in places.

On the other hand, my kids are learning from PDF’s now, and once the lesson is over, they delete the PDF’s, so they have nothing to reference - and even if they were saving them, it’d be a challenge to try to organize them in any meaningful way.

Books do have a lot of disadvantages (and I say this as someone who spends A LOT of money on books).

They are heavy, expensive, take up space, you can't search them etc.

However, I find it almost impossible to learn hard subjects from a PDF. Printed book is so much better. I wonder why.