On Writing Stephen King Analysis

After reading an essay, ‘On Writing’ by Stephen King, I was highly interested in King’s opinion about the necessity of reading and writing frequently in order to become a good writer. In King’s essay he talks about how he does not read to study and that he simply reads just to read; however, King does point out that though he is not reading to study there is still a learning process happening with everything he reads. “Every book you pick up has its own lesson or lessons, and quite often the bad books have more to teach than the good ones.” (King) Why does King have this opinion about books?
Are they bad books or bad writers, procrastinated or not well thought about, and most importantly will one want to finish read the book for any of those reasons? These are all questions that could be thought as one is reading a new book. Tara Dugan of the Millions Online Magazine stated:

A bad book, so-called, has just as much to teach us as a good book. It is often a far better teacher than any work that is uniformly artful, where excellence disguises the nuts and bolts of craft. A bad book also teaches us something a better book cannot: humility. Not the humility of resignation — that of admitting that we will never be very good at what we do, no matter how earnestly we try. Such humility can easily morph into the indulgent self-flagellation that either demands the commiseration of friends or brings our vocation to a standstill, where thereafter we are those people who petulantly claim we “could have been