I had to explain to my students that the proofs in their textbooks made no sense because they were discovered inductively in the opposite direction than they were written, and then sharpened for "elegance" in order to impress other professors so they will select the textbook. Take, for example, a typical epsilon-delta exercise from calculus. The official answer will start with "let epsilon equal blah blah bla" and the student will stop right there and scratch their head "how did they come up with that?". Well, that was the last thing they came up with.

We have met the enemy, and he is us — Pogo