I'm a former college admissions officer. The essays are a very important piece of this process and a chance for the student to truly have a voice. The committee looks at a number of different metrics to assess fit and the essays are a chance to really hear that student's voice. Typically schools want to know three things (and these questions may be answered across a number of essays): who are you (the student), do you know who we are (the school), and do you believe there is a fit between us both.
The student should be able to honestly answer these questions and if there is much struggle in attempting to do so a student should ask him/herself, "Is this school truly a good fit for me?" No lip-service in these essays; we can see right through that. Be sincere and passionate.