Another reason to be familiar with the canonical works in a culture is precisely because they’re canonical. It’s like a common currency. By now, English-speaking culture is so rooted in Shakespeare that you’d be missing out if you didn’t recognize the references.
Yes. Same reason some familiarity with the King James Version of the Bible is culturally useful.
Yes. Same reason some familiarity with the King James Version of the Bible is culturally useful.
cf Richard Dawkins on his lifelong love of the King James Bible