1. It makes up for your skimming
When you're in a rush to finish an assignment, you often end up only skimming your paper instead of truly editing and revising. This mentality can lead to skipping over little mistakes. Having someone else read your paper can often compensate for the I’ll-just-reread-it-really-fast mentality. Even though youwrote it, you should still have someone else read through it–someone who will take their time and look for local issues such as comma splices and the incorrect use of homonyms like their, there, and they’re.
2. You might be trying too hard
It's easy to go on tangents when you're trying to meet a page requirement or use a thesaurus to find bigger, fancier words to try to impress the teacher. It's also difficult, particularly when you've just left high school, to allow yourself to break free from the five-paragraph rule. When there are so many rules you're trying not to break and requirements you're trying to meet, it's hard to avoid writing a paper that is too formulaic or rambling. Someone else can let you know when you're being repetitive, or when you might need a paragraph break or a simpler word.
3. You can see how it sounds to a different audience
Professors often ask their students to write as if the reader has no prior knowledge of the subject. What better way to figure out if you accomplished this goal than to actually have someone with no prior knowledge read it?
4. Your wording might be confusing
It's easy to understand what you're trying to say when reading your own writing. When we speak, we often use phrases that others may not understand. The same thing can happen in writing. When you have someone else read your work, they can point out weird phrases–maybe you accidentally said "#yolo" without noticing it.
5. Your tone might sound off
It's hard to find the right tone when you're writing an academic paper. What's too formal? What's too informal? To ensure your tone is on point, tell someone the context of your paper and what the formality requirements are, and then let them read through it.
6. You want to make sure your paper makes sense
One of the biggest problems people have when writing papers is making sure what they’re writing makes sense to the reader. You want your paper to get your argument/message across to your reader. What makes sense to you may not make sense to another. If no one understands what you’re saying, why bother writing anything at all?