I would argue that the average program that got printed in a book was probably quite bad but still of a higher quality than the programs people wrote on their own, simply because the latter were usually written without any education or useful models of working programs.

It’s like an iceberg of bad code: the underwater part nobody saw was astonishingly terrible by modern standards. That code might be running a business, but its author would never get exposed to professional programming. Today Excel often serves a similar purpose. (Excel isn’t spaghetti though since the execution model is completely different.)