When you allow a fresh set of eyes on your admission essay it is almost as if your personal statement is getting practice. After all, your statement will ultimately end up being read by one or more people while your application is being reviewed so it makes sense that a well read personal statement should do better in its final stages. Why have the reviewers catch the mistakes that someone else can catch beforehand? It is far better to catch a small mistake that can cost you admission, before it actually has the chance to cost you.
A PS is one of the most important components of your application because this document, when written correctly, will offer your readers, namely the admissions committee members, a quick glance into your life story so far and which direction you plan to take. You are inviting the reader to share your experiences as you disclose who you are as an applicant. Through your PS, you are providing them a general picture of your background and qualifications, knowledge of which will allow them to evaluate your suitability for admission to their school accurately.