Darn teachers

I have my grades from my second semester of graduate school already posted.  I turned my 20 page paper in last monday, there are 15 people in the class, and the teacher had the grades up yesterday.  There is no way she read everyones paper and was able to grade it that quickly.  Why on earth does she make us write long papers to not even read them.  I guess I dont mind that she did not read them critically, but I feel like she probably didnt read them at all.