The Purpose of Summer reading.....?

What exactly is the purpose of summer reading? according to teachers, it's used to "prepare your minds for the new school year" otherwise known as: "Preventing your brain from turning into mush so you dont turn out to be a complete dumbass in the new  school year". how come summer reading books are almost always so fucking boring?! Why do we have to choose from a list of books that we dont want, and probably never will read, instead of just picking our own books that we actually want to read? Summer vacation is supposed to be a break from school, why do they have to assign such shitty books?! grrrrr