Plumbing doesn't work; both Sumerians and Cretans of the Minoan era had indoor plumbing to a degree.

Printing works for the same subtle reasons it led to the chaos and breaking of the Catholic Church's stranglehold on the European World. It spreads knowledge independent of one official thing, yet it also rigidizes (yes I make up words) the knowledge being dispensed. Instead of fifty hand copies with various errors and independent flourishes, you've got five hundred, each identical to the last, taking away the creativity magic might need.