Face it there are only so many spots on the roster with the school you may be looking to gain access to. Reviewers will be looking over countless application as well as countless personal statements which allows you a great opportunity to stand out from the rest by writing a statement that is leaps and bounds above the rest. By doing so, you are giving yourself a great leg up on the competition. When you go about employing the fresh eyes others to look over your personal statement before you turn it in, you will be ensuring that your one shot to impress is in fact your best shot.
As mentioned, this part of your application can be used to decide whether a school wants to invite you for an interview or not. Schools only accept students who have been invited for interviews, so getting to this step is a huge part of the process.