1) Why is it important to use an academic voice rather than a conversational

1) Why is it important to use an academic voice rather than a conversational voice in research papers.
2) What constitutes plagiarism and why is it considered the felony of academic writing?

Use APA 7 formatting.  
It is an opinion essay

It needs to be aroun 450-500 words. 
Please use at least one reference (can be the text book or some other reference).