In the Spring, the shoe will be on the other foot and schools will be hoping to be chosen over all the other schools by candidates that hold more than one offer. So, some schools want to know if you understand the school's mission and educational philosophy and why you feel you'd be a good match for that school, why it would be a good fit for you.
If you did not have a stellar undergrad record, be careful about stating that you are attracted to the school's extracurricular offerings as it could be interpreted to mean that you will put extracurriculars over academic work.
Likewise, if you lived home or close to home for college, don't list location as the reason you are most interested as it appears that you are unable to cut the apron strings. Furthermore, if there is more than one school in the area, you should have some reason besides geography, that attracts you to the school that is interviewing you today. On the other hand, if you are a state resident interviewing at a state school and you really want to practice in that state, it is a good thing to say so.