Why is knowing the parts of speech important?
This knowledge is important so that writers know how to structure sentences appropriately; different parts of speech have different functions within sentences and therefore should be used properly.
Why do some people believe that William Shakespeare didn't write his plays?
Because he started schooling at a late age and ended at an early age during a time when people from his peasant class typically didn't receive a great education.
Why do authors use rhetorical devices such as similes, metaphors, and hyperboles when they write?
These exaggerations/comparisons serve as a way to make a point clear to a reader as sometimes exaggerations/comparisons are needed when the literal word doesn't quite do the trick.