Technology gets more and more complicated in an effort to provide more and better goods at a lower cost. New technology provides impressive levels of productivity but requires very high investments. New technologies are usually very expensive and very complicated - particularly for the home experimenter.
The backyard mechanic on the other hand is not interested in productivity. If in operating his backyard foundry, he makes one casting an afternoon and enjoys what he's doing, then he does not need the new high-priced technology. Old methods will do.
The purpose of this book is to preserve old methods before they become lost forever.