"Brian Kernighan - "Unix for Beginners" (1979)"
Exactly. It was 1979 and it was for beginners - a different era, dinosaurs still dominated the IT landscape.
Careful thought stay, print statements have to go away, even for beginners which should learn how to use a debugger ASAP, and a profile not much later. Especially when they could print out sensitive data "for debugging purposes".
The problems are exactly those who still believe things should have been done like nothing changed, and whatever Kernighan & Ritchie said are holy words from the Great Zero & One themselves.... turn technology and science into a religion, and you'll litter your program with ranks of evil bugs - after all what happened with most C programs after people understood they could exploit them as vulnerabilities to p0wn systems...