Keep in mind that some schools want to see that you are actually interested. So if they give you the option of writing a 'why X law school' essay, then write it (if you want to go, obviously). Even if they don't explicitly give the option, a short 'why X' essay is still appropriate. Admissions peeps know how easy it is to apply to lots of schools and may just reject you if no connection is apparent. To me, this is the only downside (besides cost) of applying to a lot of schools: it's hard to tailor your applications to specific schools.