Why is reading William Shakespeare more important than reading Asimov; or Reader’s Digest for that matter?

This is surely the rub regarding the value of a canon. My understanding would be this: that some authors use and abuse language in such a creative way that they stretch the possibilities for all who come after them.

So, while as a devoted reader of breakfast cereal boxes I know exactly what you mean about breadth of experience, I think some writers offer us a depth of experience that is not available even by say giving a hundred typewriters to a hundred monkeys in the Readers' Digest building for a hundred years...