Well said!

To an extent, I agree to what you have said that writing is an art. If someone's writing is good, then why does he need to change that. Plus, some people might be talented storytellers without being an active readers.

However, let's hypothetically take a random group of people and ask them to write a story.
Now, if we ask this group to read everything they could from poem writers over a year and then ask them to write a story again. Do you think that some of them may have a more poetic touch to the story?

In addition, there is no reason to read for someone who is trying to copy someone else (e.g. Shakespeare). You'd just read Shakespeare's books instead.

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